Le Morte dArthur Vol. 2 Chap. 13.18
       CHAPTER XVIII. How Sir Launcelot, half sleeping and half waking, saw a sick man borne in a litter, and how he was healed with the Sangreal.

    AND so he fell asleep; and half waking and sleeping he saw come by him two palfreys all fair and white, the which bare a litter, therein lying a sick knight. And when he was nigh the cross he there abode still. All this Sir Launcelot saw and beheld, for he slept not verily; and he heard him say: O sweet Lord, when shall this sorrow leave me? and when shall the holy vessel come by me, where through I shall be blessed? For I have endured thus long, for little trespass. A full great while complained the knight thus, and always Sir Launcelot heard it. With that Sir Launcelot saw the candlestick with the six tapers come before the cross, and he saw nobody that brought it. Also there came a table of silver, and the holy vessel of the Sangreal, which Launcelot had seen aforetime in King Pescheour's house. And therewith the sick knight set him up, and held up both his hands, and said: Fair sweet Lord, which is here within this holy vessel; take heed unto me that I may be whole of this malady. And therewith on his hands and on his knees he went so nigh that he touched the holy vessel and kissed it, and anon he was whole; and then he said: Lord God, I thank thee, for I am healed of this sickness.

    So when the holy vessel had been there a great while it went unto the chapel with the chandelier and the light, so that Launcelot wist not where it was become; for he was overtaken with sin that he had no power to rise again the holy vessel; wherefore after that many men said of him shame, but he took repentance after that. Then the sick knight dressed him up and kissed the cross; anon his squire brought him his arms, and asked his lord how he did. Certes, said he, I thank God right well, through the holy vessel I am healed. But I have marvel of this sleeping knight that had no power to awake when this holy vessel was brought hither. I dare right well say, said the squire that he dwelleth in some deadly sin whereof he was never confessed. By my faith, said the knight, whatsomever he be he is unhappy, for as I deem he is of the fellowship of the Round Table, the which is entered into the quest of the Sangreal. Sir, said the squire, here I have brought you all your arms save your helm and your sword, and therefore by mine assent now may ye take this knight's helm and his sword: and so he did. And when he was clean armed he took Sir Launcelot's horse, for he was better than his; and so departed they from the cross.