A.E. Popham, The Drawings of Leonardo da Vinci (London: Random House, 1946), 252.
Drawing of a back of skeleton. This personally is my favorite drawing. Along with the bones he provides the tendons that connect the skeleton and spine, however from his drawing they are almost indecipherable. This drawing in particular really shows how da Vinci thought of the human body in a mindset akin to engineers, with lots of pulleys and other moving parts.