So vile a thing is a lie that even if it spoke fairly of God it would take away somewhat from His divinity; and so excellent a thing is truth that if… - Leonardo da Vinci

"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."

One can have no smaller or greater mastery than mastery of oneself.

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