user71532: I read the following article: 

Bitcoin surging higher after mystery trader buys $344mn in cryptocurrency, Russia Today, February 19, 2018.

Where could the man buy such a large amount of Bitcoin? On an exchange?

user4525: Such amounts will not be bought in a single transaction. Instead buying them will be spread out across different exchanges and different periods of time. If this is not done such a transaction would buy up the whole sell order book of an exchange and would run up the price through the roof.
A total of 34k bitcoins is about 3.6% of the volume of the bitcoin market in the last 24 hours. Your Russian friend is a whale by any definition for sure, but 34k bitcoin is not an impossible amount to buy.

71532: <p>I read the following article: </p>

<ul>
<li><a href="https://www.rt.com/business/419204-bitcoin-growth-mystery-investor/" rel="nofollow noreferrer">Bitcoin surging higher after mystery trader buys $344mn in cryptocurrency</a>, Russia Today, February 19, 2018.</li>
</ul>

<p>Where could the man buy such a large amount of Bitcoin? On an exchange?</p>
 4525: <p>Such amounts will not be bought in a single transaction. Instead buying them will be spread out across different exchanges and different periods of time. If this is not done such a transaction would buy up the whole sell order book of an exchange and would run up the price through the roof.</p>

<p>A total of 34k bitcoins is about 3.6% of the volume of the bitcoin market in the last 24 hours. Your Russian friend is a whale by any definition for sure, but 34k bitcoin is not an impossible amount to buy.</p>
