Warren Buffett, the billionaire investor, has been outspoken about his disdain for cryptocurrencies.  

Bitcoin is "probably rat poison squared," remarked Buffett before the Berkshire Hathaway meeting on Saturday. 

Buffett has never been a fan of any cryptocurrency. "If you buy something like bitcoin or some cryptocurrency, you don't really have anything that has produced anything. You're just hoping the next guy pays more," Buffett said in an April interview with Yahoo Finance. "You aren't investing when you do that. You're speculating. There's nothing wrong with it. If you wanna gamble somebody else will come along and pay more money tomorrow, that's one kind of game. That is not investing."

Last November, Buffett made similar remarks. "You can't value Bitcoin because it's not a value-producing asset," he said at the time.

In 2014, Buffett called bitcoin a "mirage." Back then, bitcoin was being sold for about $600. Before the Berkshire (BRK.A) - Get Report(BRK.B) - Get Report meeting on Saturday, bitcoin was nearing $10,000. 

Buffett has been wrong about cryptocurrency before. At the end of last year, bitcoin hit its all-time high of $19,500 according to Coindesk's price index. The same price index values bitcoin at $9,300 currently.

BRK.A was up 1% on Monday afternoon and BRK.B was up 0.8%.