The force of pulley-blocks and how to reckon it
A rule for finding the greatest weight a tackle can move
In mirror script Leonardo sets down a rule for gauging the office and force of pulley-blocks (taglie): to know their power you must first know the weight of the mover or of the load, then multiply the mover's weight by the number of wheels in the tackle to find the greatest weight it can raise. The reasoning treats compound pulleys as a device for multiplying force in proportion to their wheels. Below the main paragraph the sheet carries a further, shorter block of writing crossed by ruled lines that the bundle does not transcribe.
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Multiply the mover's weight by the number of wheels
To understand with certainty the office and force of pulley-blocks you must know the weight of the thing that moves or of the thing moved. Multiplying the mover's weight by the number of wheels in the blocks gives the greatest load the moving power can raise. The note frames the tackle as a means of multiplying force in proportion to its wheels.