A Treatise on Painting, by Leonardo da Vinci
Senex and Taylor, London
'Tis a thing of the last Importance, and which deserves the most mature Consideration, to chuse proper Grounds for your Figures, and to dispose your Opake Bodies in such manner as may be most advantageous to their Lights and Shadows; always taking Care that their illuminated Parts appear on dark Grounds, and their shadow'd Parts on Grounds that are more bright; an Instance of which you may find in Tab. 1. Fig. 14.