“All objects transmit their image to the eye in pyramids, and the nearer to the eye these pyramids are intersected the smaller will the image appear of the objects which cause them.”

Source: Covel, Trend Following, page 55

The Notebooks of Leonardo da Vinci (1883), I Prolegomena and General Introduction to the Book on Painting
Context: The eye — which sees all objects reversed — retains the images for some time. This conclusion is proved by the results; because, the eye having gazed at light retains some impression of it. After looking (at it) there remain in the eye images of intense brightness, that make any less brilliant spot seem dark until the eye has lost the last trace of the impression of the stronger light.

The Notebooks of Leonardo da Vinci (1883), II Linear Perspective
Context: The body of the atmosphere is full of infinite radiating pyramids produced by the objects existing in it. These intersect and cross each other with independent convergence without interfering with each other and pass through all the surrounding atmosphere; and are of equal force and value — all being equal to each, each to all. And by means of these, images of the body are transmitted everywhere and on all sides, and each receives in itself every minutest portion of the object that produces it.

The Notebooks of Leonardo da Vinci (1883), II Linear Perspective

Source: The Prime Minister (1876), Ch. 37

Pylyshyn (1981, 18-19), as cited in: Ken Clements, "Visual imagery and school mathematics." For the learning of mathematics 2.2 (1981): 2-9.

Source: Materialism and Empirio-Criticism (1908), p. 116

The Notebooks of Leonardo da Vinci (1883), II Linear Perspective

Source: Image and Mind. 1980, p. 51