Cheng Hao
However, the king continuously called Yi Hwang back and unable to refuse further, he resumed office at the age of 68 and wrote many advisory documents including "Seonghak sipdo" (hangul:성학십도, hanja:聖學十圖, "Ten Diagrams on Sage Learning"). He also gave lectures from the teachings of Song Dynasty Confucian scholars Cheng Yi and Cheng Hao, I Ching, Analects, and Zhang Zai in royal presence. He finally retired from politics at the age of 70 and died in 1570.