The passage made by the solar rays through the angular aperture necessarily takes up some space… The sun passes round through the angle and makes an intersection, and upon the flat face it produces another effect.

a a — a a

At whatever point the convergence of the solar rays passes, an intersection must necessarily occur. Make the parts of the surface of impact equidistant from the aperture, and the parts of the aperture equidistant from the sun, and you will see the effects in perfection.

m n — c a — d b — o p. The circle np is made by the angle d.

It is necessary that the intersections of the round pyramids be made at a single point, enclosed by a non-transparent circumference. The intersection made by the half-round pyramid must be made at a point closed only on the half side. It is impossible for the intersection of the square pyramid to pass through a single point.

No angle can be carried from the sphere of the sun onto the object. A thing smaller than the pupil, placed close to it, behaves as does a thing seen from 20 braccia, which lies within the angle of convergence of the visual lines.

The solar ray, the farther it moves from the intersection, the more it grows.

The straight line is farther from the spherical body than any other line. The spherical body is more like the spherical body than anything else. The universal intersection cannot occur except at a single point, and the angle ends in a point.

This aperture, having no angle, will never cast upon the object an impression of the nature of its cause. The intersection of the round pyramids must be made at a single point closed on every side. The intersection made by the half-round pyramids must likewise be made at a single point, closed only on one side, which point you will find at the angle. And if you touch your eyes with the angle inside the set-square, the angle will seem to you to be in the form of a half circle. And when the convergence of the rays is as far from the intersection at its end as it is from the intersection to their cause, the rays will have spread out as at the beginning. If you make a solar image formed in a cross-shaped aperture pass, and before it becomes round make it pass through a round aperture, it will afterward return to a cross.

f a e — d b — g c h. At the distance of 20 braccia you will lose the parts e, f, g, h, and by 30 braccia a spherical body will have been formed of the parts a, b, c, d, because the part that lies toward the centre is the more powerful.