Royal Collection (RLW), 19008r; K/P 140r
In the studies of the knee and ankle joints on this sheet, Leonardo consistently resorts to the analogy with the lever. In an annotation, he describes the Achilles tendon as a lever that raise the heel using the fore part of the foot as a fulcrum (top right figure), and measures the tendon's exact strength by applying the laws of levers. The lower left figure shows the leg complete with the muscles whose mechanical actions control the movements of the limb.
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