Even the richest soil, if left uncultivated will produce the rankest weeds.

For those colours which you wish to be beautiful, always first prepare a pure white ground.

The merit of painting lies in the exactness of reproduction. Painting is a science and all sciences are based on mathematics. No human inquiry can be a science unless it pursues its path through mathematical exposition and demonstration.

Knowledge ... shall always bear witness like a clarion to its creator.

Truly man is the king of beasts, for his brutality exceeds them. We live by the death of others. We are burial places.

Learning is the only thing that never disappoints us.

If a man has a tent made of linen of which the apertures have all been stopped up, and be it twelve bracchia across (over twenty-five feet) and twelve in depth, he will be able to throw himself down from any height without sustaining injury. [His concept of the parachute.]