I thought I was learning to live; I was only learning to die. - Leonardo da Vinci

Oh! human stupidity, do you not perceive that, though you have been with yourself all your life, you are not yet aware of the thing you possess most of, that is of your folly? and then, with the crowd of sophists, you deceive yourselves and others, despising the mathematical sciences, in which truth dwells and the knowledge of the things included in them. And then you occupy yourself with miracles, and write that you possess information of those things of which the human mind is incapable and which cannot be proved by any instance from nature. And you fancy you have wrought miracles when you spoil a work of some speculative mind, and do not perceive that you are falling into the same error as that of a man who strips a tree of the ornament of its branches covered with leaves mingled with the scented blossoms or fruit.

Simplicity is the ultimate sophistication.
When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.
Learning never exhausts the mind.
Art is never finished, only abandoned.
Painting is poetry that is seen rather than felt, and poetry is painting that is felt rather than seen.
The human foot is a masterpiece of engineering and a work of art.
It had long since come to my attention that people of accomplishment rarely sat back and let things happen to them. They went out and happened to things.
I have been impressed with the urgency of doing. Knowing is not enough; we must apply. Being willing is not enough; we must do.
As a well-spent day brings happy sleep, so a life well spent brings happy death.
Water is the driving force of all nature.

I myself have proved it to be of no small use, when in bed in the dark, to recall in fancy the external details of forms previously studied, or other noteworthy things conceived by subtle speculation; and this is certainly an admirable exercise, and useful for impressing things on the memory.