Emperor Yūryaku
Compiled sometime after 759, the oldest poetic anthology of waka is the 20 volume "Man'yōshū", in the early part of the Heian period, it gathered ancient works. The order of its sections is roughly chronological. Most of the works in the "Man'yōshū" have a fixed form today called chōka and tanka. But earlier works, especially in Volume I, lacked such fixed form and were attributed to Emperor Yūryaku.