4013215A Treatise on Painting — Of the Painter’s WindowJohn Francis RigaudLeonardo da Vinci

Chap. CCL.Of the Painter’s Window.

The window which gives light to a painting-room, ought to be made of oiled paper, without any cross bar, or projecting edge at the opening, or any sharp angle in the inside of the wall, but should be slanting by degrees the whole thickness of it; and the sides be painted black.