On the choice of a position (536-537)
536.
HOW HIGH THE POINT OF SIGHT SHOULD BE PLACED.
The point of sight must be at the level of the eye of an ordinary man, and the farthest limit of the plain where it touches the sky must be placed at the level of that line where the earth and sky meet; excepting mountains, which are independent of it.
537.
OF THE WAY TO DRAW FIGURES FOR HISTORICAL PICTURES.
The painter must always study on the wall on which he is to picture a story the height of the position where he wishes to arrange his figures; and when drawing his studies for them from nature he must place himself with his eye as much below the object he is drawing as, in the picture, it will have to be above the eye of the spectator. Otherwise the work will look wrong.
The apparent size of figures in a picture (538-539)
538.