A Treatise on Painting, by Leonardo da Vinci
Senex and Taylor, London
The Bone and Cartilage which compose the Nose, may be varied Eight different ways, which Form as many different kinds of Noses; for either they are equally streight, equally concave, and equally convex, which is the first kind; or they are streight, concave, and convex unequally, which is the second; or the Parts above are streight, and those below concave, which is the third sort; or those above are streight, and those below convex, and this is the fourth sort; or else they are concave above, and streight below, and this is the fifth; or concave above, and convex below, which makes the sixth; or lastly, they are convex above, and streight below, which is the seventh; or convex above, and concave below, which is the eighth kind. The setting on of the Nose to the Eye-brows, admits but of two different Forms, for it is always, either concave or streight. The Forehead is capable of three various Shapes, being either plain, concave, or convex; the plain is again divided several ways, for it is either hollow towards the top, or towards the bottom, or it is so, both at top and bottom; or else it is plain and uniform, both at top and bottom.