In which era was the four tones first used to write poems?

In the following year of Qi Yong in the Southern Dynasty, Zhouyi wrote "Four Tones Cut Rhyme" and proposed to enter the same level of four tones. Shen Yue, together with Xie Tiao, Wang Rong, Fan Yun and others, combined the division of four tones with traditional poetry rhyme and rhyme knowledge, and stipulated a set of prosodic defects that should be avoided in the creation of five-character poems, namely "eight diseases" recorded in later generations. That is, flat head, upper tail, bee waist, crane knee, big rhyme, small rhyme, side button and straight button, and the specific causes of the eight diseases are different. The theory of "four tones and eight diseases" laid the foundation for later modern poetry.