early as in 1492 Leonardo's writing in perspective was so far advanced that he could quote his own statements.—As bearing on this subject compare what is said in No. 280.] And the reason of this is shown in my [book on] perspective.
561.
OF SHADOWS.
Where a shadow ends in the light, note carefully where it is paler or deeper and where it is more or less indistinct towards the light; and, above all, in [painting] youthful figures I remind you not to make the shadow end like a stone, because flesh has a certain transparency, as may be seen by looking at a hand held between the eye and the sun, which shines through it ruddy and bright. Place the most highly coloured part between the light and shadow. And to see what shadow tint is needed on the flesh, cast a shadow on