"I have always felt it incumbent upon me to describe each thing in the most exact way possible: to always ask — how does this actually work?"

"The eye is the window of the human body through which it feels its way and enjoys the beauty of the world."

"Perspective is the bridle and rudder of painting."

"Motion is the cause of every life."

"Shadow is the privation of light and it appears to me that it is the most subtle and the hardest to study of any science."

"Shun those studies in which the work that results dies with the worker."

"Nothing can be desired that is more excellent than the union of eyes and ears, which gives the perfection of all knowledge."

"He who thinks little errs much."

"Tell me if anything was ever done. Tell me if anything was ever done."