Billionaire investor Warren Buffett has revealed he was in the bathtub when he dreamt up the idea to invest $5bn in the faltering Bank of America.

Like Sicilian mathematician Archimedes who proved the best ideas are bathtub-based, the Berkshire Hathaway owner told CNBC he got the idea to approach BofA CEO Brian Moynihan with the investment offer while bathing on Wednesday morning.

BofA said yesterday that it would sell Berkshire Hathaway’s investment fund 50,000 shares of preferred stock with a six per cent annual dividend.

Buffett injected struggling companies like Goldmach Sachs and General Motors with similar cash investments during the height of the financial crisis.