Thou, O God, dost sell us all good things at the price of labor.

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

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.]

O painter skilled in anatomy, beware lest the undue prominence of the bones, sinews and muscles cause you to become a wooden painter from the desire to make your nude figures reveal all.

A bird is an instrument working according to mathematical law, which instrument it is within the capacity of man to reproduce with all its movements.

Human subtlety will never devise an invention more beautiful, more simple or more direct than does nature because in her inventions nothing is lacking, and nothing is superfluous.

It is the infinite alone that cannot be attained, for if it could it would become finite.