The visual pyramid and the apparent size of objects
Object m appears larger than n as the pyramid's width b d exceeds a c
The closing lines of a perspective demonstration state that an object m will appear larger than an object n in the same proportion as the width of the visual pyramid b d exceeds that of a c. Below the text two small diagrams show visual pyramids drawn in profile, each tapering from a broad base toward a point and lettered to match the argument. The header reads 'PARTE', the running head of this section of Leonardo's Treatise on Painting.
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Apparent size governed by the width of the visual pyramid
The passage concludes that object m appears greater than object n by exactly as much as the base b d of its visual pyramid exceeds the base a c of the other. Apparent magnitude is thus tied directly to the breadth of the pyramid of sight that each object subtends at the eye.
Two visual pyramids drawn in profile
Below the text are two small triangular figures, each narrowing from a base at one end toward a single point at the other, representing the pyramids of sight referred to in the argument. Their bases and vertices carry the letters a, c, b and d used in the demonstration.