Musannaf Ibn Abi Shaybah

Hazrat Hasan bin Amr's father narrates that he saw Hazrat Saeed bin Jubair performing prayer while sitting in the "Habwah" position. When he was about to go into ruku (bowing), he would untie the Habwah, then stand up and perform ruku. (The meaning of making Habwah is that a person sits on his buttocks with his knees raised and ties both hands around them for support, or ties a cloth around his back and knees. The people of Arabia often used to sit in this manner.)