cause; means

interpretations of the trigrams

Zhong Yao (151-230), minister of Cao Wei 曹魏[Cao2 Wei4] and noted calligrapher, said to have developed the regular script 楷書|楷书[kai3 shu1]

Zhang Sengyou (active c. 490-540), one of the Four Great Painters of the Six Dynasties 六朝四大家