Weight, and the swiftness of the eye, sun-ray, and mind
A beam carried upstairs, the sun's three powers reaching the eye, and a two-finger touch illusion
A text-only leaf mixing statics, optics, and the psychology of the senses. Leonardo argues that the part of an elongated heavy body farthest from its centre weighs less, and that of two men carrying a beam up a stair the lower man bears more; a body hung from one end weighs more than when slung from both. He then ranks the eye, the sun's ray, and the mind as the swiftest of motions: the sun's rays reach from east to west carrying splendour, heat, and the species of their form, the opened eye takes in all the stars of the hemisphere at once, and the mind leaps instantly across the world. A closing experiment on the sense of touch shows that a round object felt with two crossed fingers seems to be two.
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The far end of a long weight is the lighter
The part of a heavy elongated body that lies farthest from the centre, though of equal thickness, will be the lighter. Hence of two men carrying a beam up a stair the lower one bears more weight, and the same body hung from one end weighs more than when suspended from both.
The sun's ray carries three spiritual powers to the eye
The eye, the sun's ray, and the mind are named the swiftest of all motions. The moment the sun appears in the east it runs with its rays to the west, and those rays are composed of three spiritual powers: splendour, heat, and the species of the form of their cause.
The opened eye takes in every star of the hemisphere
As soon as it is opened, the eye sees all the stars of our hemisphere at once, and the mind leaps in an instant from east to west. Other spiritual things are said to be far slower in speed than these.
The eye retains the images of luminous things
Leonardo notes that the eye keeps within itself the images of the luminous things presented to it, the persistence of vision that recurs across these folios as evidence that images enter and remain in the eye.
A round thing felt by two crossed fingers seems double
If you set the second finger beside the third so that its whole nail passes to the other side, whatever is touched by the two fingers will seem two, provided the thing touched is round. It is offered as a proof about the sense of touch.