Here is the translation of what Leonardo da Vinci annotated around his drawing in mirror writing:
"Vitruvius says, in his work on architecture: Nature has distributed the measurements of the human body like this:
Four fingers make a palm, and four palms make a foot, six palms make an elbow: four elbows make the height of a man. And four elbows make a double step, and twenty-four palms make a man; and he used these measures in his constructions. See more
If you open your legs so as to lower your height by one fourteenth, and if you extend your arms so that the tips of your fingers are at the top of your head, you must know that the centre of your extended limbs will be at the navel, and the space between your legs will be an equilateral triangle.
The length of a man's outstretched arms is equal to his height.
From the hairline to the bottom of the chin, there is one tenth the height of a man. From the bottom of the chin to the top of the head, an eighth. From the top of the chest to the top of the head, a sixth; from the top of the chest to the hairline, a seventh.
From the nipples to the top of the head, a quarter of the man's height. The greatest width of the shoulders is contained within a quarter of a man's height. From the elbow to the tip of the hand, a quarter. From the elbow to the armpit, one eighth.
The whole hand is one tenth of a man. The birth of the manly limb is in the middle. The foot is a seventh of the human being. From the sole of the foot to below the knee, a quarter of a man. From below the knee to the beginning of the genitals, a quarter of a man.
The distance from the bottom of the chin to the nose, and from the roots of the hair to the eyebrows is the same, as is the ear: one third of the face.