The Da Vinci Notebooks at sacred-texts.com
Propositions on perspective of disappearance from MS. C. (250-262).Of several bodies of equal size and equally distant from the eye, those will look the smallest which are against the lightest background.
Every visible object must be surrounded by light and shade. A perfectly spherical body surrounded by light and shade will appear to have one side larger than the other in proportion as one is more highly lighted than the other.