Math and Knitting

From Elizabeth Zimmermann's description of her Pi Shawl:

Have you begun to see the well-known geometric theory behind what you have been doing? If you are a man, you will have spotted it right away. If you are a woman (sorry, lib), you probably expunged such theories from your memory the minute you finished high school, or even college, to make room or more useful stuff. It's Pi; the geometry of the circle hinging on the mysterious relationship of the circumference of a circle to its radius. A circle will double its circumference in infinitely themselves-doubling distances, or, in knitters' terms, the distance between the increase-rounds, in which you double the number of stitches, goes 3, 6, 12, 24, 48, 96 rounds, and so on to 192, 394, 788, 1576 rounds for all I know. Theory is theory, and I have no intention of putting it into practice, as I do not plan to make a lace carpet for a football field.