Two or three buttons, but will not carry more than four

Read in the NYT (1996):

On the eve of the Wright brothers' historic first flights in 1903, Simon Newcomb, an eminent United States scientist, predicted that the first successful flying machine would be the handiwork of a watchmaker and would carry nothing heavier than an insect. Later he increased the payload: ''It may carry two or three buttons, but will not carry more than four.'' And so it goes. "

More in "The Experts Speak : The Definitive Compendium of Authoritative Misinformation" (Christopher Cerf, Victor S. Navasky)