Dividing a circle into seven, and a chamber of eight mirrors
Compass constructions dividing a circle, and an octagonal room of eight mirrors giving endless reflections.
The upper and middle of the sheet give compass constructions: how to divide a circle into seven equal parts, and how to build a circle that contains nine of a given line. At the lower right Leonardo sketches a man standing inside an octagonal booth. The accompanying note describes lining such a chamber with eight flat mirrors so that the man within sees himself reflected infinitely in every direction.
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Dividing a circle into seven equal parts
After drawing the circle, the compass point set at c gives the line a d, and set at d gives a c; the line a b, falling on the middle of the line c d, is then exactly one seventh of the whole circle.
A circle containing nine of a given line a b
Upon the line a b a circle is to be built that contains nine of these lines within it; placing h b at g n makes the point g the centre of the circle.
A man amid eight mirrors: the octagonal mirror chamber
Eight flat mirrors, each 2 braccia wide and 3 tall, set in a circle to compose an octagon sixteen braccia around and 5 braccia in diameter, let a man standing inside see himself in every direction an infinite number of times. Four mirrors set in a square, Leonardo adds, would also serve.