Suspended beam and a ball on an inclined plane
The times of motion m n and n b stand in the ratio of the distances
The upper diagram is a graduated horizontal beam with two hanging weight-boxes, annotated with the numbers 12, 4, 10, 6, 9. The lower diagram shows a ball at the apex of a right triangle, with a base line running from p to m and the ball dropping toward n and b. Leonardo states a proportion of motion: the ratio of the distance n b to the distance m n equals the ratio of the time of the motion along m n to the time of the motion along n b.
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Times of motion along the inclined and horizontal paths
A ball at the apex commands two paths, m n and n b. Leonardo asserts that the proportion the length n b has to m n is the same proportion that the time of the motion m n has to the time of the motion n b, relating the distances travelled to the times of travel.
Numbers of the suspended beam
The upper graduated beam carries the sequence of figures 12, 4, 10, 6, 9, laid off along its length as the loads and divisions of a balance of the kind worked out on the neighbouring folios.