Scanned the two pages of test work I did before the final drawing too. They're here and here.
Mostly was just a test. Thinking of doing some drawings where instead of single lead lines making up the knot with intersections being just one lead going over the other... using a twisted pair double lead line for the entire thing, with every intersection being a weave of 4 leads. So I wanted to test different ways of intersecting twisted pairs... hence the center of the square.
*shrug* Just random.