From About.com: "A soap maker at the Procter and Gamble company had no idea a new innovation was about to surface when he went to lunch one day in 1879. He forgot to turn off the soap mixer, and more than the usual amount of air was shipped into the batch of pure white soap that the company sold under the name The White Soap. Fearing he would get in trouble, the soap maker kept the mistake a secret and packaged and shipped the air-filled soap to customers around the country. Soon customers were asking for more "soap that floats." When company officials found out what happened, they turned it into one of the company's most successful products, Ivory Soap."