Perspective: the air full of infinite radiant pyramids
Leonardo's optics of vision, with a diminishing triangle for measuring by distance
Under the heading 'Prospettiva', this irregularly cut fragment sets out Leonardo's theory of vision: the body of the air is filled with infinite radiant lines and pyramids, each carrying the likeness of the object that causes them, intersecting and interweaving without hindering one another, so that every least part of the air holds the whole image. A long narrow triangle at the right, numbered 4 / 2 / 1 and marked 'measure by distance', illustrates proportional diminution. A rayed disk and a small conical form are drawn at centre-left, and the Ambrosiana's classification links the sheet to studies of the sun, moon and earth and of eclipses, pointing to further untranscribed matter.
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The air filled with infinite radiant pyramids
The body of the air is full of infinite radiant lines and pyramids, caused by the object placed within it, which represent to other objects the form of their cause. Intersected and interwoven without occupying one another, they pour through all the surrounding air; they are of equal power, so that all can do as much as each and each as much as all, and the likeness of the body is carried whole through the whole and whole in each part.
Measure by distance: the diminishing triangle
A tall, narrow triangle at the right of the sheet is stepped off with the numbers 1, 2, 3, 4 and inscribed 'measure by distance'. It sets out how apparent size diminishes in proportion to remoteness, the geometric core of linear perspective.
Rayed disk and further untranscribed notes
Additional mirror-script fills the sheet beyond the transcribed passages, alongside a small rayed disk and a conical form drawn at centre-left. The Ambrosiana's classification associates this material with the sun, moon and earth, their orbits and phases, and the difference between solar and lunar eclipses.