With this study, Leonardo wants to demonstrate in practice that wings can sustain weights. He believes that if the long lever is pushed down fast enough, the connected wing will lift a bench as heavy as a man. Studying the ratio between the weight and the wingspan of a duck, Leonardo calculates that this wing should measure about 12 metres in width and length. This makes it very difficult to manoeuvre for one man alone.
Manuscript B, sheet 88 v. 1483-86