'Foolish' Idea: A box which keeps drinks - such as milk - fresh.
How Idea was Launched:
Ruben patented his box-shaped beverage container 30 years ago. He marketed it through his business, Tetra Pak - turning it into one of the world's largest and most profitable paper-packaging businesses.
Ruben retired and his two sons, Gad and Hands took over the reins in the early 1980's. The business is now called Tetra Laval, since the £1.5billion take-over of Alfa Laval in 1991. Gad bought Han's 50% shareholding in 1995.
Earnings: Ruben's earnings from his invention, not known. His son Hans's proceeds from selling his shares in the business is reckoned to have been about £3billion.