CXCV
You should choose an old tumbledown wall and throw over it a piece of white silk. Then morning and evening you should gaze at it, until at length you can see the ruin through the silk—its prominences, its levels, its zigzags, and its cleavages, storing them up in the mind and fixing them in the eye. Make the prominences your mountains, the lower parts your water, the hollows your ravines, the cracks your streams, the lighter parts your nearer points, the darker parts your more distant points. Get all these thoroughly into you, and soon you will see men, birds, plants, and trees, flying and moving among them. You may then ply your brush according to your fancy, and the result will be of heaven, not of men.
Sung Ti (Chinese, eleventh century).
CXCVI
By looking attentively at old and smeared walls, or stones and veined marble of various colours, you may fancy that you see in them several compositions—landscapes, battles, figures in quick motion, strange countenances, and dresses, with an infinity of other objects. By these confused lines the inventive genius is excited to new exertions.
Leonardo.