Koormasana (Tortoise Pose)
Ghudam nirudhya ghulphabhyam vyutkramena samahitah/
Kurmasanam bhavedetaditi yogavido viduh//(Chapter -1, Verse 22).
Press the anus firmly with the ankles in the opposite direction and sit well-poised. According to the Yogis this is called as Koormasana. (Chapter -1, Verse 22).