When you put your hand in a flowing stream, you touch the last that has gone before and the first of what is still to come.

To me it seems that those sciences are vain and full of error which are not born of experience, mother of all certainty, first-hand experience which in its origins, or means, or end has passed through one of the five senses.

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

As every divided kingdom falls, so every mind divided between many studies confounds and saps itself.

It should not be hard for you to stop sometimes and look into the stains of walls, or ashes of a fire, or clouds, or mud or like places, in which...you may find really marvellous ideas.

Test knowledge through experience, be prepared to make mistakes, and be persistent about it.

Nature is so delightful and abundant in its variations that among trees of the same kind there would not be found one which nearly resembles another, and not only the plants as a whole, but among their branches, leaves, and fruit, will not be found one which is precisely like another.