>>41438839
>A Chinese legend concerning the pre-historic Emperor Yu (夏禹) tells of the Lo Shu, often in connection with the Yellow River Map (Hetu) and the eight trigrams. In ancient China there is a legend of a huge deluge: the people offered sacrifices to the god of one of the flooding rivers, the Luo river (洛河), to try to calm his anger. A magical turtle emerged from the water with the curiously unnatural Lo Shu pattern on its shell: circular dots representing the integers one through nine are arranged in a three-by-three grid.

https://en.wikipedia.org/wiki/Luoshu_Square