user3631: U Ba Khin, in IMC: Personal Experiences of Candidates, writes some quite interesting "explanatory remarks" about the experiences that Mr. J. Van Amersfoort had during a meditation course. 
In those remarks U Ba Khin sees the Parajikan Atthakatha as an authoritative treatise which talks about the "realization of the Truth by an analysis of the kalapas in the body with the lens of Samadhi obtained through Anapana Sati". 
I was not able to find the text of that Parajikan Atthakatha, as far I could gather it should be a Vinaya commentary. Does someone have a full English translation of it? I would be interested in how it deals with kalapas.

user7555: Not sure if able to follow, since the question does not provide much further explaining, but Atma could think, that it recognizes the importance that one actually has to face and investigate the circle of birth, aging, death and rebirth as a phenomena seeing within one self, which seem like never been mentioned by the Buddha, speaking of death, moment for moment (kalapa means also time of existence or life).
The Commentary especially the Visuddhimagga, gives much arguments to focus on that and not keeping it different form depending co-arising.

user3631: Monk Sarana has been so kind to let me know the existence of an English translation he is aware of (now out of print but digitalized by him):
Shan-Chien-P'i-P'o-Sha
A Chinese version by Sanghabhadra of Samantapasadika,
Commentary on Pali Vinaya translated into English for the first time
By Prof. P. V. Bapat, Poona
in collaboration with Prof. A. Hirakawa, Tokyo
Bhandarkar Oriental Research Institute, Poona, 1970

This is a complete translation of the Chinese version of the Vinaya Commentary, so not exactly corresponding to the Burmese version that U Ba Khin could have used.
The Anapana section starts from page 358 to 381 of the PDF file. I was not able to find a passage similar to what U Ba Khin was mentioning. A possibile candidate may be the following, where after emergence from strong samadhi (fourth jhana) one contemplates its physical base:
[20] [How does he stabilise it? This Bhikkhu emerges from the Fourth
trance. He- firmly grasps the factors of the trance. When he has grasped
this, [he sees that] these factors of trance are depending upon the heartbasis
which, in turn, is based upon the Four Great Elements; the contemplation
upon Four Great Elements is [also] based upon his physical
body. Out of these, the factors of a trance are called non-material and(heart-)
basis and the rest material. The non-material dhammas are to cover consciousness.
Out of these [dhammas ], the Four Great Elements and the like
are material and mind accompanying those material qualities, is nonmaterial.
Or, when he emerges from the samadhi, he notices that the body
and mind are the source ( ... ) of the out-going and in-coming breath.

Incidentally but interestingly, what should be the same passage as translated from the Visuddhimagga and reported in the other answer is here rendered differently:

Thus -he has discriminated Name from Form and then he seeks their
  causal factors. In all the three worlds, the Name and Form are
  inseparably joined; they are never severed [from each other].
  Regarding this inseparable connection, he begins to have some doubt.
  But he overcomes that and then notices three characteristic marks.
  Having noticed these three characteristic marks, he further reflects
  upon the coming into and passing out of existence. Because of this
  contemplation upon the coming into and passing out of existence, he
  first notices the [illusion of] light and gets rid of the ten minor
  taints of the penetrating insight (vipassana'). [22] When he has got
  rid of them, there appears the Knowledge of the Path (...). When this
  has appeared, he abandons thinking of the coming into existence and
  has his attention directed only to the passing out of existence. Then
  he again and again reflects upon that characteristic of the passing
  out of existence and when these two dhammas (coming into and passing
  out of existence) have now become clear to him, he begins to have a
  sense of aversion [for all things] in this threefold world. And then
  in due succession, he attains the Four Paths and reaches the Fruit of
  Arhatship. He attains the highest stage of the nineteen types of deep
  knowledge (...) and in this threefold existence consisting of Brahmas,
  Maras, and Samana-Brahmanas, he reaches the highest stage of being the
  field of merit (...). Thus is concluded the first tetrad of the
  detailed explanation of the mindfulness of Anapana [commencing with ]
  counting.

Also as we can see (in bold) the word "kalāpasammasanavasena" (if even present in the Chinese version) is interpreted differently. Bhikkhu Ñánamoli rendered that as "comprehension by groups", and it seems not related to the kalapas as groups of the four elements, that is to what U Ba Khin was intending.

user295: This (Parajikan Atthakatha) is available within Samantapāsādikā more particularly the part called Parajikakanda Atthakatha. The original is published by PTS and available in Pali at the Pariyatti Store. As for an English translation there is: The Inception of Discipline & the Vinaya Nidana: Being a Translation & Edition of the Bahiranidana of Buddhaghosa's Samantapasadika, the Vinaya Commentary (Sacred Books of the Buddhists). (Link to Inception of Discipline N.A. Jayawickrama at Pariyatti Store) I am not sure if this is complete and thorough thought as the original is a 8 volume set which seems to be condensed to 1 volume in the English translation. If you are looking fro free editions both (Pali and english) are available in https://archive.org/ which I have given the links above.
Probably U Ba Khin is referring to the following passage (PDF from Parajikakanda Atthakatha, page 160):

Evaṃ nāmarūpaṃ vavatthapetvā tassa paccayaṃ pariyesati, pariyesanto ca taṃ disvā tīsupi addhāsu
  nāmarūpassa pavattiṃ ārabbha kaṅkhaṃ vitarati. Vitiṇṇakaṅkho kalāpasammasanavasena tilakkhaṇaṃ āropetvā
  udayabbayānupassanāya pubbabhāge uppanne obhāsādayo dasa vipassanupakkilese pahāya upakkilesavimuttaṃ
  paṭipadāñāṇaṃ ‘‘maggo’’ti vavatthapetvā udayaṃ pahāya bhaṅgānupassanaṃ patvā nirantaraṃ bhaṅgānupassanena
  bhayato upaṭṭhitesu sabbasaṅkhāresu nibbindanto virajjanto vimuccanto yathākkamaṃ cattāro ariyamagge
  pāpuṇitvā arahattaphale patiṭṭhāya ekūnavīsatibhedassa paccavekkhaṇañāṇassa pariyantappatto sadevakassa lokassa
  aggadakkhiṇeyyo hoti. Ettāvatā cassa gaṇanaṃ ādiṃ katvā vipassanāpariyosānā ānāpānassatisamādhibhāvanā ca samattā hotīti.

That turns out to be a quote from Visuddhimagga (viii-224 and viii-225), part of a commentary on the first tetrad of anapana meditation. The English Bhikkhu Ñánamoli’s translation is the following:


Having defined mentality-materiality in this way, he seeks its condition. With search he finds it, and so overcomes his doubts about
  the way of mentalitymateriality’s occurrence in the three divisions of
  time (Ch. XIX). His doubts being overcome, he attributes the three
  characteristics [beginning with that of suffering to mentality and
  materiality], comprehending [them] by groups (XX.2f.); he abandons the
  ten imperfections of insight beginning with illumination, which arise
  in the first stages of the contemplation of rise and fall (XX.105f.),
  and he defines as “the path” the knowledge of the way that is free
  from these imperfections (XX.126f.). He reaches contemplation of
  dissolution by abandoning [attention to] arising. When all formations
  have appeared as terror owing to the contemplation of their incessant
  dissolution, he becomes dispassionate towards them (Ch. XXI), his
  greed for them fades away, and he is liberated from them (Ch. XXII).
  After he has [thus] reached the four noble paths in due succession and
  has become established in the fruition of Arahantship, he at last
  attains to the nineteen kinds of reviewing knowledge (XXII.19f.), and
  he becomes fit to receive the highest gifts from the world with its
  deities.
At this point his development of concentration through mindfulness of breathing, beginning with counting and ending with
  looking back (§189) is completed.



3631: <p>U Ba Khin, in <a href="http://pariyatti.org/Treasures/tabid/104/Default.aspx" rel="nofollow" title="IMC: Personal Experiences of Candidates">IMC: Personal Experiences of Candidates</a>, writes some quite interesting "explanatory remarks" about the experiences that Mr. J. Van Amersfoort had during a meditation course. </p>

<p>In those remarks U Ba Khin sees the <strong>Parajikan Atthakatha</strong> as an authoritative treatise which talks about the "<em>realization of the Truth by an analysis of the kalapas in the body with the lens of Samadhi obtained through Anapana Sati</em>". </p>

<p>I was not able to find the text of that Parajikan Atthakatha, as far I could gather it should be a Vinaya commentary. Does someone have a full English translation of it? I would be interested in how it deals with kalapas.</p>
 7555: <p>Not sure if able to follow, since the question does not provide much further explaining, but Atma could think, that it recognizes the importance that one actually has to face and investigate the circle of birth, aging, death and rebirth as a phenomena seeing within one self, which seem like never been mentioned by the Buddha, speaking of death, moment for moment (kalapa means also time of existence or life).</p>

<p>The Commentary especially the <a href="http://www.accesstoinsight.org/lib/authors/nanamoli/PathofPurification2011.pdf" rel="nofollow">Visuddhimagga</a>, gives much arguments to focus on that and not keeping it different form depending co-arising.</p>
 3631: <p>Monk Sarana has been so kind to let me know the existence of an <a href="https://archive.org/details/ShanChienPiPoShaSanghabhadrasChineseSamantapasadikatr.ByProf.P.V.BapatAndProf.A.Hirakawa" rel="nofollow noreferrer">English translation</a> he is aware of (now out of print but digitalized by him):</p>

<pre><code>Shan-Chien-P'i-P'o-Sha
A Chinese version by Sanghabhadra of Samantapasadika,
Commentary on Pali Vinaya translated into English for the first time
By Prof. P. V. Bapat, Poona
in collaboration with Prof. A. Hirakawa, Tokyo
Bhandarkar Oriental Research Institute, Poona, 1970
</code></pre>

<p>This is a complete translation of the Chinese version of the Vinaya Commentary, so not exactly corresponding to the Burmese version that U Ba Khin could have used.</p>

<p>The Anapana section starts from page 358 to 381 of the PDF file. I was not able to find a passage similar to what U Ba Khin was mentioning. A possibile candidate may be the following, where after emergence from strong samadhi (fourth jhana) one contemplates its physical base:</p>

<pre><code>[20] [How does he stabilise it? This Bhikkhu emerges from the Fourth
trance. He- firmly grasps the factors of the trance. When he has grasped
this, [he sees that] these factors of trance are depending upon the heartbasis
which, in turn, is based upon the Four Great Elements; the contemplation
upon Four Great Elements is [also] based upon his physical
body. Out of these, the factors of a trance are called non-material and(heart-)
basis and the rest material. The non-material dhammas are to cover consciousness.
Out of these [dhammas ], the Four Great Elements and the like
are material and mind accompanying those material qualities, is nonmaterial.
Or, when he emerges from the samadhi, he notices that the body
and mind are the source ( ... ) of the out-going and in-coming breath.
</code></pre>

<p>Incidentally but interestingly, what should be the same passage as translated from the Visuddhimagga and reported in the other answer is here rendered differently:</p>

<blockquote>
  <p>Thus -he has discriminated Name from Form and then he seeks their
  causal factors. In all the three worlds, <strong>the Name and Form are
  inseparably joined; they are never severed [from each other]</strong>.
  Regarding this inseparable connection, he begins to have some doubt.
  But he overcomes that and then notices three characteristic marks.
  Having noticed these three characteristic marks, he further reflects
  upon the coming into and passing out of existence. Because of this
  contemplation upon the coming into and passing out of existence, he
  first notices the [illusion of] light and gets rid of the ten minor
  taints of the penetrating insight (vipassana'). [22] When he has got
  rid of them, there appears the Knowledge of the Path (...). When this
  has appeared, he abandons thinking of the coming into existence and
  has his attention directed only to the passing out of existence. Then
  he again and again reflects upon that characteristic of the passing
  out of existence and when these two dhammas (coming into and passing
  out of existence) have now become clear to him, he begins to have a
  sense of aversion [for all things] in this threefold world. And then
  in due succession, he attains the Four Paths and reaches the Fruit of
  Arhatship. He attains the highest stage of the nineteen types of deep
  knowledge (...) and in this threefold existence consisting of Brahmas,
  Maras, and Samana-Brahmanas, he reaches the highest stage of being the
  field of merit (...). Thus is concluded the first tetrad of the
  detailed explanation of the mindfulness of Anapana [commencing with ]
  counting.</p>
</blockquote>

<p>Also as we can see (in bold) the word "kalāpasammasanavasena" (if even present in the Chinese version) is interpreted differently. Bhikkhu Ñánamoli rendered that as "comprehension by groups", and it seems not related to the kalapas as groups of the four elements, that is to what U Ba Khin was intending.</p>
 295: <p>This (Parajikan Atthakatha) is available within <a href="https://store.pariyatti.org/Samantapasadika-Vol-1_p_2142.html" rel="nofollow">Samantapāsādikā</a> more particularly the part called <a href="https://archive.org/details/1.PrrjikakakaaAhakath" rel="nofollow">Parajikakanda Atthakatha</a>. The original is published by PTS and available in Pali at the <a href="https://store.pariyatti.org/Samantapasadika-Vol-1_p_2142.html" rel="nofollow">Pariyatti Store</a>. As for an English translation there is: <a href="https://archive.org/details/sacredbooksofbud21londuoft" rel="nofollow">The Inception of Discipline &amp; the Vinaya Nidana: Being a Translation &amp; Edition of the Bahiranidana of Buddhaghosa's Samantapasadika, the Vinaya Commentary (Sacred Books of the Buddhists)</a>. (Link to <a href="https://store.pariyatti.org/Inception-of-Discipline_p_2151.html" rel="nofollow">Inception of Discipline</a> N.A. Jayawickrama at Pariyatti Store) I am not sure if this is complete and thorough thought as the <a href="https://store.pariyatti.org/Samantapasadika-8-Volume-Set_p_2150.html" rel="nofollow">original is a 8 volume set</a> which seems to be condensed to <a href="https://store.pariyatti.org/Inception-of-Discipline_p_2151.html" rel="nofollow">1 volume in the English translation</a>. If you are looking fro free editions both (Pali and english) are available in <a href="https://archive.org/" rel="nofollow">https://archive.org/</a> which I have given the links above.</p>

<p>Probably U Ba Khin is referring to the following passage (<a href="https://archive.org/details/1.PrrjikakakaaAhakath" rel="nofollow">PDF from Parajikakanda Atthakatha, page 160</a>):</p>

<blockquote>
  <p>Evaṃ nāmarūpaṃ vavatthapetvā tassa paccayaṃ pariyesati, pariyesanto ca taṃ disvā tīsupi addhāsu
  nāmarūpassa pavattiṃ ārabbha kaṅkhaṃ vitarati. Vitiṇṇakaṅkho <strong>kalāpasammasanavasena</strong> tilakkhaṇaṃ āropetvā
  udayabbayānupassanāya pubbabhāge uppanne obhāsādayo dasa vipassanupakkilese pahāya upakkilesavimuttaṃ
  paṭipadāñāṇaṃ ‘‘maggo’’ti vavatthapetvā udayaṃ pahāya bhaṅgānupassanaṃ patvā nirantaraṃ bhaṅgānupassanena
  bhayato upaṭṭhitesu sabbasaṅkhāresu nibbindanto virajjanto vimuccanto yathākkamaṃ cattāro ariyamagge
  pāpuṇitvā arahattaphale patiṭṭhāya ekūnavīsatibhedassa paccavekkhaṇañāṇassa pariyantappatto sadevakassa lokassa
  aggadakkhiṇeyyo hoti. Ettāvatā cassa gaṇanaṃ ādiṃ katvā vipassanāpariyosānā <strong>ānāpānassatisamādhibhāvanā</strong> ca samattā hotīti.</p>
</blockquote>

<p>That turns out to be a quote from Visuddhimagga (<a href="http://thepathofpurification.blogspot.it/2011/09/visuddhimagga-viii-224.html" rel="nofollow">viii-224</a> and <a href="http://thepathofpurification.blogspot.it/2011/09/visuddhimagga-viii-225.html" rel="nofollow">viii-225</a>), part of a commentary on the first tetrad of anapana meditation. The English <a href="http://sites.google.com/site/chewdhamma/PathofPurification2011.PDF" rel="nofollow">Bhikkhu Ñánamoli’s</a> translation is the following:</p>

<blockquote>
  <ol start="224">
  <li>Having defined mentality-materiality in this way, he seeks its condition. With search he finds it, and so overcomes his doubts about
  the way of mentalitymateriality’s occurrence in the three divisions of
  time (Ch. XIX). His doubts being overcome, he attributes the three
  characteristics [beginning with that of suffering to mentality and
  materiality], comprehending [them] by groups (XX.2f.); he abandons the
  ten imperfections of insight beginning with illumination, which arise
  in the first stages of the contemplation of rise and fall (XX.105f.),
  and he defines as “the path” the knowledge of the way that is free
  from these imperfections (XX.126f.). He reaches contemplation of
  dissolution by abandoning [attention to] arising. When all formations
  have appeared as terror owing to the contemplation of their incessant
  dissolution, he becomes dispassionate towards them (Ch. XXI), his
  greed for them fades away, and he is liberated from them (Ch. XXII).
  After he has [thus] reached the four noble paths in due succession and
  has become established in the fruition of Arahantship, he at last
  attains to the nineteen kinds of reviewing knowledge (XXII.19f.), and
  he becomes fit to receive the highest gifts from the world with its
  deities.</li>
  <li>At this point his development of concentration through mindfulness of breathing, beginning with counting and ending with
  looking back (§189) is completed.</li>
  </ol>
</blockquote>
