Iron rusts from disuse; water loses its purity from stagnation... even so does inaction sap the vigor of the mind.

Avoid studies of which the result dies with the worker.

An arch consists of two weaknesses which, leaning one against the other, make a strength.

Perspective is nothing more than a rational demonstration applied to the consideration of how objects in front of the eye transmit their image to it, by means of a pyramid of lines. The Pyramid is the name I apply to the lines which, starting from the surface and edges of each object, converge from a distance and meet in a single point.

How painting surpasses all human works by reason of the subtle possibilities which it contains.

He who does not understand the supreme certainty of mathematics is wallowing in confusion.

Life well spent is long.