Six one-pound weights and their counterweights
An equilibrium problem, with a two-toothed key gripping mechanism
Folio 99r poses an equilibrium problem: six weights a b c d e f hang from a horizontal shaft, each meant to weigh one pound, and Leonardo asks what variety of counterweights should be set against them at g h i K l m to hold everything in balance. The large upper drawing shows the six suspended loads slung from the shaft. A lower figure treats a key mechanism in which a plate lets two parts be gripped separately by the two teeth of the key.
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Balancing six one-pound weights with counterweights
Leonardo proposes six weights a b c d e f, each of one pound, and asks what counterweights must be placed against them at g h i K l m to stand in equilibrium. The upper drawing shows the six loads hung in pairs from a horizontal shaft.
A plate letting a key grip with two teeth
The lower note explains that a n stand upon n, and in the middle goes a plate, so that the parts are gripped separately by the two teeth of the key. The adjacent figure shows the corresponding lever-and-key device.