Tears come from the heart and not from the brain

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.

Whoever in debate quotes authority uses not intellect, but memory.

A good painter has two main objects to paint, man and the intention of his soul. The former is easy, the latter hard as he has to represent it by the attitude and movement of the limbs.

Study me, reader, if you delight in me, because on very few occasions shall I return to the world, and because the patience for this profession is found in very few, and only in those who wish to compose things anew. Come, oh men, to see the miracles that such studies will disclose to nature.

If you throw a stone in a pond... the waves which strike against the shores are thrown back towards the spot where the stone struck; and on meeting other waves they never intercept each other's course... In a small pond one and the same stroke gives birth to many motions of advance and recoil.

Mechanics is the paradise of the mathematical sciences because by means of it one comes to the fruits of mathematics.