The Auspicious Pose / Perfect Pose - Siddhasana
Svastikasana 
Meditation Posture

Siddhasana is lauded as one of the ideal poses for meditation and with remarkable effects for the practitioner's energetic control, and when mastered, culminates in an effortlessly occurring samadhi.  

The left foot is brought and placed with the heel towards or under the perineum, then the right foot is placed into the fold of the left leg, with the heels stacking off set from one another. Traditionalists often insist the right leg should be placed on top for the best energetic effect as the right side is the dynamic and controlling aspect, therefor better at directing energy. Like the other postures of meditation the feet are turning upward and more under the body. Siddhasana is the pose that most completely creates this effect, and this is why it is said to greatly stimulate the nadis and activate the central channel. The energy of the two sides, balanced through this infinity like position of the legs, is brought directly underneath of sushumna.

The final alignment of the pose in which you are actually sitting on your heel requires significant external rotation and abduction of the hips. Poses like One Leg Pigeon, Wide Split, Frog, Warrior II, Baddha Konasana, and Vertical Wide Split will help create the necessary flexibility. 

It may be advised for practitioner's to practice the pose with a block to main a level pelvis and the proper curvatures of the spine. For men, one heel is below the genitals and the other above. Those who are not quite in the final position may also find it more comfortable to sit on the block.