Compound levers built from toothed wheels and pulleys
A geared train and a many-pulley tackle balanced at 33 pounds
The upper figure is a row of toothed wheels with pinions on vertical axles, weighted at each end; the notes explain that this arrangement works like a set of simple levers of equal number, except that its geared teeth give it a continuous motion the simple lever lacks. The lower figure is a long frame reeved with many pulleys (girelle), marked m-n and f. Leonardo states that multiplying the number of pulleys by the counterweight f yields the balancing weight m n of 33 pounds. He judges this many-pulley tackle the weakest of compound hauls but the safest, because it has no gear teeth.
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Toothed wheels giving continuous motion
This mode resembles the levers shown opposite with an equal number of axles, but because it is built from toothed wheels with their pinions it has continuity in its motion. The simple-lever instrument is deprived of that continuous action.
Many-pulley tackle in equilibrium at 33 pounds
Multiplying the number of pulleys by the pounds of the counterweight f gives the weight m n, which stands in equilibrium with f at 33 pounds. Among compound hauls this is the weakest but the safest, since it is not subject to the teeth of wheels like the others.
Ratios of the geared train
The upper figure is annotated with a repeated series of numbers reading 1, 10, 1, 10 across the train, expressing the step-down ratio taken at each geared stage. The multiplication of pulley count by counterweight in the lower note follows the same proportional reasoning.