Here it is shown how to make a quadrangle, and from it to make an octagon.

g S - h - d a r b - c - e - f - p m

Here is shown the quick way to make a square and divide it into 8 equal parts. First make the line d e, then set the compasses on point d and make the line g f; then set the compasses on point e and make the line h m; then draw the line s p up through the 2 intersections; then set the compasses at the middle of the cross, at point c, and make a circle; and where this circle cuts the arms of the cross, there you will make the corners of your square; then take the measure from b c and set it on a b, and set that same measure on d r; and do likewise on each face, and you will have divided the square into 8.

Here it is taught how, upon the given line a b, to make a square and an octagon.

M p - f c m - a S b - d - o n - n o

If you wish to divide a circle quickly into 8 equal parts, first make the line a b; then put one of the compass points on point a and make the line M n; then put the other point on b and make the line o p; then, from the 2 intersections made by the 2 curved lines, draw the line c d, and 4 right angles will be made at the centre S, on which you will fix one compass point and make your circle, which will remain divided into 4 equal parts; then take the half of one of these parts, and with that measure divide the other 3, that is f o n; and from 4 there will be made eight faces.

m

If you keep a household in the house, arrange their quarters so that at night neither they nor any strangers you may lodge are masters of the exit of the house, and so that they cannot enter the rooms where you live and sleep. Close the door m, and you have shut up the whole house.