Warren Buffett hasn't shied away from letting his opinion of cryptocurrencies be known. Now he's doubled down on his skepticism of the digital assets.<br />Speaking to CNBC anchor Becky Quick ahead of Berkshire Hathaway's annual meeting in Omaha, Nebraska on Saturday, the billionaire investor said bitcoin is "probably rat poison squared." Bitcoin is the largest and most well-known cryptocurrency.<br />Earlier this year, the 87-year-old said bitcoin would "definitely come to a bad ending. <br />
