IMHO, the "yin-yang" is a seifert minimal surface on a trefoil knot.
Using the flat crossing knot diagram of the trefoil knot, showing two holes, the "braid" type,
there is a procedure to make a seifert surface by replacing the crossings by bands rotated 90 degrees.
Unrotating the central band orients the two holes to 90 degrees, and the flat surface becomes 3D.

- Brian