they weren’t sure how he measured it but he left notes;

quote“In his characteristic mirror script, Leonardo wrote: ‘If you open your legs enough that your head is lowered by one-14th of your height and raise your hands enough that your extended fingers touch the line of the top of your head, know that the center of the extended limbs will be the navel, and the space between the legs will be an equilateral triangle’,” Mac Sweeney points out.