“Traditionally, Fu Xi is considered the originator of the I Ching (also known as the Yi Jing or Zhou Yi), which work is attributed to his reading of the He Map (or theYellow River Map). According to this tradition, Fu Xi had the arrangement of the trigrams (八卦 bāgùa) of the I Ching revealed to him supernaturally. This arrangement precedes the compilation of the I Ching during the Zhou dynasty. He is said to have discovered the arrangement in markings on the back of a mythical dragon horse (sometimes said to be a turtle) that emerged from the Luo River. This discovery is said to have been the origin of calligraphy. Fu Xi is also credited with the invention of the Guqin musical instrument, though credit for this is also given to Shennong and Huangdi.”

From Wikipedia, information about Fu Xi, who some consider to have been a mythological character.

Fu Xi, with the 8 trigrams and a turtle, as imagined by the Song painter Ma Lin