Siddhasana
Siddhasana (Sanskrit: सिद्धासन; IAST: siddhāsana) or Accomplished Pose is an asana, also known as ardha - padmasana where ardha is sanskrit word for half.
The name comes from the Sanskrit words siddha (सिद्ध; siddha) meaning both "perfect" and "adept", and asana (आसन; āsana) meaning "posture" or "seat".
Description
From a seated position, one heel is brought to the groin area (perineum), then the opposite ankle placed over the first leg with the toes and heel of the second foot resting in the fold made between the thigh and calf of the first leg beneath it. The spine is held erect. A small meditation cushion or zafu is sometimes used to aid vertical back alignment. Usage
Siddhasana and Padmasana (Lotus Pose) are the two asanas traditionally used for dhyana (meditation) and pranayama (breath) exercises. Sukhasana (Pleasant Pose) is a substitute that is easier on the knees. Many people are not able to practice Padmasana for them Siddhasana is highly recommended.
The Hatha Yoga Pradipika asks, When siddhaasana is mastered, of what use are the various other postures?