Says David Twicken about the He Tu Diagram:
"This Taoist cosmological model contains energetic pairings that can be used to identify relationships in the practice of acupuncture. From an Eight Extraordinary Channel perspective, the He Tu provides the theory for coupled pairs.
In the center are five dots. Five represents the center, core, yuan or primordial; number patterns in each direction are multiples of five, which is the Earth element. This diagram reveals that all elements, numbers and directions originate from the center or earth."
Various He Tu combinations create the other four elements, and form the basis for the Eight Extraordinary Channel coupled pairs.
While Fu Xi was credited with discovering the He Tu Diagram, it was Yu the Great who received - as a reward from Heaven - the Luo Sho Diagram, as described here by Mr. Twicken:
"Yu the Great was rewarded by Heaven for his many positive contributions to humanity. Out of the river a horse-dragon appeared with special markings on its back. Those marks are the Luo Shu. The Luo Shu has many applications in the Taoist arts; for example, flying stars feng shui, meridian clock theory, nine star astrology and neidan - internal alchemy."