As a means of practising this perspective of the variation and loss or diminution of the proper essence of colours, take at distances, a hundred braccia apart, objects standing in the landscape, such as trees, houses, men, and places, and in front of the first tree fix a piece of glass so that it is quite steady, and then let your eye rest upon it and trace out a tree upon the glass above the outline of the tree; and afterwards remove the glass so far to one side that the actual tree seems almost to touch the one
that you have drawn. Then colour your drawing in such a way that the two are alike in colour and form, and that if you close one eye both seem painted on the glass and the same distance away. Then proceed in the same way with a second and a third tree, at distances of a hundred braccia from each other. And these will always serve as your standards and teachers when you are at work on pictures where they can be applied, and they will cause the work to be successful in its distance. But I find it is a rule that the second is reduced to four-fifths the size of the first when it is twenty braccia distant from it.
Leonardo.
CXXII
The great and golden rule of art, as well as of life, is this: That the more distinct, sharp, and wiry the bounding line, the more perfect the work of art.... Great inventors in all ages knew this: Protogenes and Apelles knew each other by this line; Raphael and Michael Angelo, and Albert Dürer, are known by this and this alone. The want of this determinate and bounding form evidences the idea of want in the artist's mind.
Blake.
CXXIII
My opinion is that he who knows how to draw well and merely does a foot or a hand or a neck, can paint everything created in the world; and yet there are painters who paint everything there is in the world so