くひんわか
新編国歌大観V.229, 日本歌学大系１
A collection of 18 poems divided into 9 ranks, compiled by Fujiwara no Kinto around 1009. The rankings were repeated in a number of later treatises such as the 奥儀抄.
すぐれたる事もなくわろき所もなくてあるべきさまをしれるなり
春きぬと人はいへどもうぐひすのなかぬかぎりはあらじとぞおもふ