Leonardo's genius as an engineer rests on three foundations.

1. He saw how the design of machines must rest on mathematical laws of physics, and not rely on practice. For instance, he realised that the power of an unwinding spring diminished according to a mathematical ratio.
2. He was the first to design separate components that could be used in several devices such as gears for barrel springs and ring bearings for axles.
3. He drew machines with more attention to reality. His efforts to devise various kinds of flying machines were directed by applying the principles of a bird in flight.

The reality is no less exciting. He was trained in Florence in the 1470s. During that time, workshops of the major artists included art in every kind of medium and tasks we would now consider engineering.

These artist-engineers were employed to produce a wide range of practical machines suc...