The body which is nearest to the light casts the largest shadow, and why? If an object placed in front of a single light is very close to it you will… - Leonardo da Vinci

The painter strives and competes with nature...There is nothing in all nature without its reason. If you know the reason, you do not need the experience...

"Further than this, influenced by Platonic thought, Leonardo's conception of painting was, as an intellectual state or condition, outwardly projected. The painter who practised his art without reasoning of its nature was like a mirror unconsciously reflecting what was before it. Although without a "manual act" painting could not be realized, its true problems — problems of light, of colour, pose and composition, of primitive and derivative shadow — had all to be grasped by the mind without bodily labour. Beyond this, the scientific foundation in art came through making it rest upon an accurate knowledge of nature. Even experience was only a step towards attaining this."

The air which is struck with most swiftness by the movable thing is compressed to the greatest degree in itself.