Drawing is based upon perspective, which is nothing else than a thorough knowledge of the function of the eye.

It is a far worthier thing to read by the light of experience than to adorn oneself with the labors of others.

A man of supreme folly: his life flies away while he is merely hoping to enjoy it.

Every action done by nature is done in the shortest way.

Although nature commences with reason and ends in experience it is necessary for us to do the opposite, that is to commence with experience and from this to proceed to investigate the reason.

You do ill if you praise, but worse if you censure, what you do not understand.

A bird maintains itself in the air by imperceptible balancing, when near to the mountains or lofty ocean crags; it does this by means of the curves of the winds which as they strike against these projections, being forced to preserve their first impetus bend their straight course towards the sky with divers revolutions, at the beginning of which the birds come to a stop with their wings open, receiving underneath themselves the continual buffetings of the reflex courses of the winds.