"If you want to see the true proof of the wings, make a wing out of paper, using a framework out of canes and master canes, for a widht and length of at least 20 braccia. And fix it over a heavy board weighing 200 pounds, and make a rapid force, as shown above. And if the board weighing 200 pounds lift up before the wing lowers, the proof is good. But make it so that the force is swift, and if this effect does not succeed, do not lose more time with it."
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 the weight of a man. Studying the ratio between the weight and the wingspan of a duck, Leonardo calculates that this wing should measure about 20 braccia (12 metres) in width. This makes it very difficult to manoeuvre for one man alone.
The model is based on the drawing:
- Manuscript B f. 88 v. (1486-1487)
Paris, Institut de France