Sighting Grid
Leonardo da Vinci
Circa 1500
From the Codex Atlanticus: “Have a piece of glass as large as a half sheet of royal folio paper and set thus firmly in front of your eyes, that is, between your eye and the thing you want to draw. Then place yourself at a distance of 2/3 of a braccia from the glass fixing your head with a machine in such a way that you cannot move it at all. Then shut or entirely cover one eye and with a brush or red chalk draw upon the glass that which you see beyond it; then trace it on paper from the glass, afterwards transfer it onto good paper, and paint it if you like, carefully attending to the aerial perspective.”
(Royal Folio is about A4 or Letter Size, so the suggested size is 15 x 20 cm, and braccia is a measure of length, ‘arm’ in Italian, equal to 66-69 cm).
Note: The Codex Atlanticus is a 12-volume set of bound original drawings made by Leonardo between 1478 and his death in 1519. A complete digital scan of all Leonardo's drawings can be found here.
Source: Codex Atlanticus, 1478-1519