Those men who are inventors and interpreters between Nature and Man, as compared with boasters and declaimers of the works of others, must be regarded and not otherwise esteemed than as the object in front of a mirror, when compared with its image seen in the mirror. For the first is something in itself, and the other nothingness. — Folks little indebted to Nature, since it is only by chance that they wear the human form and without it I might class them with the herds of beasts.
The Notebooks of Leonardo da Vinci (Richter, 1888) - I Prolegomena and General Introduction to the Book on Painting