Proem on the primacy of perspective and the nature of light
A treatise's opening: perspective preferred above all human disciplines, and light retained by the eye
The sheet is filled with a sustained prologue in which Leonardo exalts perspective as the science of the radiant line, to be preferred above all human discourses and disciplines, joining the certainty of mathematics to the study of physics. He announces that he will compress the subject into conclusive brevity, weaving natural and mathematical demonstrations and dividing the work into three parts. He then states that light, acting on bright bodies and in vision, retains something of their species, so that after gazing at an intense light the eye still holds its likeness and makes darker places seem dark. Two small groups of crossed lines lettered o - o appear below.
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Perspective preferred above all disciplines
Among natural studies light most delights its contemplators, and among mathematics the certainty of demonstration most raises the mind; therefore perspective, the field of the radiant line, is to be set before all human discourses and disciplines, its glory belonging as much to physics as to mathematics. Leonardo says he will divide the work into three parts.
Light retained by the eye
Light, acting on clear and splendid things turned against it and in the act of vision, retains something of their species. This is proved by effect: after gazing at an intense light, the likeness remains in the eye and makes a place of lesser light seem dark until the impression fades.
Crossed-line ray figures
At the foot of the sheet are two small groups of intersecting lines, each marked with the letter o. They accompany the discussion of the radiant line but are not otherwise described in the text.