Perspective: the diminution of the visual pyramid over distance
Dividing a base of 48 once, planets read by reflected light, and the honoured tomb of Archimedes
Both leaves are headed 'Perspective' and work out, in extensive proportion arithmetic, how the visual pyramid diminishes with distance: a pyramid one mile long on a base of 4 braccia (48 once) is divided into fifteen 200-braccia parts, and the rule (48 once divided by 15 gives 3 1/5 once) is extended to pyramids of up to 100 miles. A lettered figure divides the base i e into equal quarters (h d, x c, a b, and i h at m). Folio 279v also digresses into optics and astronomy — reflected motion being greater than incident, and a scheme to read a planet's 'complexion' from its reflected light through an opened roof — and into a prose eulogy of Archimedes honoured by the Romans and by Cato. Diagrams and further untranscribed calculations fill both leaves.
On this page
The visual pyramid narrowing with distance
Leonardo sets a pyramid one mile long on a base of 4 braccia and asks how much it narrows at 200 braccia from the base, extending the rule to a series of pyramids from one mile up to a hundred miles on the same base.
Dividing 48 once by fifteen
Because a mile of 3000 braccia contains the 200-braccia part 15 times, the base of 48 once is divided by 15 to give 3 1/5 once of narrowing at 200 braccia; for two miles (30 pairs of hundreds) it becomes 1 3/5 once, and so on.
Equal division of base and axis
A lettered figure divides the base i e of the pyramid into quarters matched to the length: the part h d narrows 1/4 of the base f e, x c another quarter g f, a b another quarter, and at m the quarter i h, so base and axis are divided equally.
Reflected light, and reading a planet's nature
A digression holds that the reflected motion of incorporeal powers can be longer and more powerful than the incident, unlike corporeal motions; and proposes opening a roof to show a single planet to a base, whose reflected light would reveal that planet's complexion.
