The document discusses Warren Buffett's investment in American Express in the 1960s when the company was embroiled in a "salad oil scandal" where it was defrauded of $150 million, causing its stock price to drop significantly. Buffett believed the market was overreacting and that American Express' "travelers checks" represented an attractive source of low-cost financing, as the company had to pay no interest on the funds and they served as a perpetual, revolving source of capital. This discovery of the value of "float" led Buffett to see it as an important competitive advantage for companies.