The Song of Buttocks (臀) in the Nine Songs of Xing Yi Quan (形意拳九歌) by Jiāng Róngqiáo (薑容樵)

臀

提起臀部，
氣貫四梢，
兩腿繚繞，
臀部肉交，
低則勢散，
故宜稍高。

薑容樵

"Raise the buttocks,
The qi will go through the four extremities
Both legs curl up.
The buttocks muscles come together.
If too low the posture is broken.
Therefore it is suitable to raise it slightly."

From the book Xing Yi Mother Fists (形意母拳), by Jiāng Róngqiáo (薑容樵), based on the translation by Joseph Crandall