Courtesy of LeonardoDaVinci.net

In this study, Leonardo has placed a block under the occipital bone to keep the head level and show it as it would be in a live model. He has drawn all the sutures and cavities accurately and with a sense of their definition. Any art student who has had to draw the skull can appreciate the outstanding proportion of this drawing. Leonardo emphasizes hollows and edges where they need it, and softens the emphasis where the outline or edge is less definite.