When the thing taken into union is perfectly adapted to that which receives it, the result is delight and pleasure and satisfaction.

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.

Learning never exhausts the mind.

The human being, creature of eyes, needs the image.

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.

Those who condemn the supreme certainty of mathematics feed on confusion, and can never silence the contradictions of the sophistical sciences which lead to eternal quackery.

Men wrongly lament the flight of time, blaming it for being too swift; they do not perceive that its passage is sufficiently long, but a good memory, which nature has given to us, causes things long past to seem present.