Four Books on Human Proportion

B ij

Furthermore, you shall establish this rule—though I do not follow it in every instance—in the following way. Draw a triangle a-b-c. Let side a-b be the horizontal original: transuersum side. Let b-c be a vertical side, positioned so that b forms a right angle. Next, divide the vertical side b-c into three equal spaces using two points, d and e. From angle a, draw two straight lines to points d and e. By this method, you will derive the proportion I mentioned.

On a measuring rod original: regula, mark with two points the length of the entire body between the middle of the collarbone original: jugulum and the bottom of the thigh original: femur. Similarly, further down, mark the bottom of the ankle original: talum below the shin original: tibia. Label the point for the collarbone f, the bottom of the thigh g, and the bottom of the ankle h. Afterward, apply the rod so that point g touches line a-d of the aforementioned triangle. Do not move this point from that line; however, rotate the rod across those lines until point f reaches the triangle’s line a-c, and until the lowest point h reaches the horizontal line a-b.

Once this is finished, line a-e will intersect the rod between g and h. At that intersection, mark the point j. You will then find three proportional measurementsanalogicas; measurements that relate to one another through a consistent ratio designated alongside the length of the body. For the ratio of the space f-g to the space g-j is the same as the ratio of space g-j to space j-h. By point f, you should understand the top of the middle of the collarbone; by point g, the bottom of the thigh; by point j, the middle of the knee original: genu; and by point h, the bottom of the ankle below the shin. While doing this, notice that the rod applied to the triangle must be tilted with point f turned upward toward the vertical side c-b. You may call such a triangle an equator equalizeræquatorem; a geometric instrument for finding means or balanced proportions. You can also use this calculation in reverse when you wish to invert a figure. Truly, it will provide great utility for the achievement of many things to those who use it correctly.