1503, on the 12th day of May / Vincenzo [da] Ziroso di Vincento is to have for this 38 1/2 of … men's buckles in the German fashion … N S 9 florins, 12 soldi, 6 denari / Item, on the 30th day of June, to have for this 12 1/2 buckles / for men, 3 florins, 2 soldi, 6 denari / Item, on the 2nd of September, this 14 buckles, no. … / … 3 florins, 1 …

Saw, for the anatomy, a head at the eyebrows, to find the cause of the equal motion of the eyes, which is almost confirmed to have as its cause the intersection of the optic nerves — that is, [the cause] of the equality of the motion. If the eyes look closely at the parts of a circle, they have nerves that make them perform a circular motion.

200 –100 100
* Among wheels of equal diameter, that one is of easier revolution which is supported by the smaller pivot.

50 –300 –150 150
If the diameter of the pivot enters 6 times into the diameter of its wheel, which is of a weight of 300 pounds, the support of that pivot feels the same weight.

400 pounds –400 –400

The whole weight of the wheels is sustained by the supports of their pivots; and by as much as those pivots enter by diameter into the diameter of the wheel, by so much does the weight of that wheel diminish for its mover.

2000 pounds – 200 – 100

Here, because the diameter of the pivot enters 20 times into the diameter of the wheel, the 2000 pounds of that wheel, which load upon the pivot, return to the mover as 100 pounds.

b a

Example of small and large pivots.
If there be 2 men who hold these ends of the staff a b, and each exerts a force of 100 pounds, the one who turns the thick part will exert a force 4 times that of the one who turns the thin part, because the thin one enters by diameter 4 times into the diameter of the thick one.

1–2–3–4
* That wheel will be of easier movement the diameter of whose pivot enters more times into the diameter of that wheel.

* The middle of every pivot …
* The lower half of the thickness of any pivot is the last degree of the contact that can load its support.

I ask, of these 3 wheels, which will be of the longest motion, being moved by an equal force.

f a – c

That pivot which, without change of position, uses of itself the smaller contact with its support will be of easier revolution.

Among pivots of variable position, that one is of easier revolution whose centre lies further outside the perpendicular of the contact it has with its support, when the motion is descending.

But if the pivot of variable position be raised upward by its motion, it is of the more difficult revolution the further its centre lies outside the perpendicular of the contact it has with its support.