The Skull Series Inside and Out

Leonardo da Vinci began his anatomical drawings arounf 1489 with that of the skull. He drew the skull based on the dissections he was able to complete. He work is admirred for its accuracy and proportion; taking specific interst of the different angles and cross-sections of the complicated boney stucture. He even goes on to draw and number the different type and positions of the teeth. 

Sources:

Skull: Takac, B. (2019). The Life of Leonardo da Vinci examined through 12 Seminal Drawings. Wide Walls.