Four Books on Human Proportion

...be longer and stronger than the front [upper] ones, as can be observed in humans. I take the torso original: "leib," here referring to the trunk to be a long part, although assembled from many pieces, yet undivided, and powerful enough to move the other limbs. These three lengths should hold themselves proportionately to one another: just as the length of the torso relates to the upper leg, so should the length of the upper leg relate to the length of the shinbone. However, I do not use this in all figures; I shall do it thus:

I draw a triangle $a.b.c$. Let $a.b$ be the horizontal side, and $b.c$ the vertical side, so that $b$ remains a right angle. Then I divide the vertical side $b.c$ with two points, $d$ and $e$, into three equal fields, and draw two straight lines from angle $a$ to the two points $d$ and $e$. From this, I seek the proportion as follows:

I take a straightedge original: "richtscheit" and mark upon it with two points the length of the torso, between the hollow of the throat and the end of the hip. Likewise, below that, the end of the outer bony bump original: "knorren," referring to the lateral malleolus or ankle bone at the bottom of the shinbone. I label the top point of the hollow of the throat with an $f$, the end of the hip with a $g$, and the end of the shinbone with an $h$. Then I take this straightedge and place point $g$ on line $a.d$ of the aforementioned triangle. I do not let this point move from that line, yet I slide the straightedge back and forth on the line until the top point $f$ touches the triangle’s line $a.c$ and the bottom point $h$ touches the horizontal line $a.b$. Once I have done this, the line $a.e$ intersects the straightedge between $g$ and $h$ and, together with the length of the torso, creates three proportionate parts. I mark this point with an $i$. Thus it follows: as the length $f.g$ relates to the length $g.i$, so also does the length $g.i$ relate to the length $i.h$.

Thus, I mark at point $f$ the height of the hollow of the throat; at point $g$ the end of the hip; at point $i$ the middle of the knee; and at point $h$ the end of the shinbone. It is also to be noted that when I place my straightedge in the triangle, I incline the top at point $f$ toward the vertical side $c.b$. This triangle may well be called a proportional divider original: "vergleicher," a tool or method for ensuring consistent ratios. This method can also be used in reverse if one wishes to invert something. This method also draws many other useful things into the work for those who can use it correctly. Now I apply this height $i$ to the figure I am drawing later, and place the knee at that same spot; then I measure further.

From the middle of the knee upwards onto the knee: a 21st part.

From the middle of the knee downwards:
{ two 19th parts; there I end the outer calf.
{ an 8th part; there I end the inner calf.

And before I go further, I will draw this triangle—the "proportional divider"—here opposite.

A large, calligraphic decorative flourish in ink at the bottom of the page, consisting of interlocking loops and a sweeping horizontal tail.