Correct method for measuring any distance.

a — d n. Plant your cane of 4 braccia in the ground, leaning as appears here, and at its upper extremity n tie the thread a d, and then make another one like this after it; and these will be the true and correct sights.

Tower - K – q – p S g t f – m. If you wish to know the truth of any distance, have with you 7 canes as straight as you can, and use them as appears in the figure above. Set q m apart by a space of 12 braccia from one another; then look that the point of the sight you have taken on the tower, and q m likewise, are on one line with your eye. Then take a thin little cord and take the space between q m; then double the said cord into equal parts and set the doubled fold joined at the foot of the cane m, and the 2 other ends, of equal length, will take exactly the middle between q m, in which middle plant the cane p. Then tie the thread again to the cane m and with the other end touch the cane q exactly, and draw a quarter-circle until you have passed the crossing of p. Then untie the cord from m and tie it to the cane q and make that same quarter-circle from m to the crossing of p, and you will see the arcs make an intersection as appears at point 5, and there set another cane. Then move away along the line p S for a space of 100 braccia as far as the point f, and take care to make f S p lie on a straight line. Then turn toward the sight of the tower and plant the cane K about 5 braccia from f, placing it so that f K and the point of the tower are in line. Then turn along the line f p and set on the same line the stake g about 3 braccia from f, and tie to it a thin cord and draw it as far as f; then turn it as far as K, then bring it back to the line f p, shifting the head of the thread r that remains in your hand so much toward f that the 2 faces of the square are touched by the right angle made by the intersection of the threads; and as much as f r goes into r K, so much do the hundred braccia between f p go into p and exactly to the point of the tower.