How the eye judges size; the moon's diameter and lustre
Optical notes on seeing small spheres and the new moon, amid mechanical sketches
An optical and astronomical page interleaved with mechanical sketches. Leonardo notes that the eye seeing a spherical body smaller than its own pupil sees it larger beyond its diameter, and more generally that the eye sees a thing smaller than itself as larger than it truly is. Turning the sheet, a sphere of the moon with a pyramid of visual rays accompanies remarks that the moon is never seen in its whole diameter (the sun more so), that the new moon's ring is much smaller than the moon's body, and that a spherical body takes on lustre only in a small part. The lower and right areas carry drawn gears, wheels, a crank and a rough textured sphere that the bundle does not transcribe, plus a 'Salai' name doodle with numbers in another hand.
On this page
A sphere smaller than the pupil is seen larger beyond its diameter
The eye, seeing a spherical body smaller than its pupil, will see it larger beyond the diameter than at the diameter itself.
The eye sees a small thing as larger than it is
The eye, seeing a thing smaller than itself, sees it larger than it actually is - illustrated by the accompanying figure.
The moon is never seen in its full diameter; the sun more so
The moon is never seen in its whole diameter, but much less; and the sun more so. A sphere of the moon with a pyramid of visual rays is drawn beside the note when the sheet is turned.
The new moon's ring is smaller than the moon's body
The moon that remains within its circle when it is new is much smaller than the body of the moon.
A spherical body takes lustre only in a small part
No body apt to take on lustre can take that lustre except in a small part, if it is spherical.
Sketches of geared wheels and a crank mechanism
The lower and right portions of the sheet carry rapidly drawn mechanical parts - toothed wheels, a large disc, cylindrical rollers and a crank - which the bundle does not transcribe; they are recorded here only as drawn, not read.