Shna means six and mukha means mouth.
In this mudra, one tries to look into oneself due to the habit of one's own existence, so it got its name.
Following are the steps to perform 'Shnmukhi mudra'
Sit in Padmasana keeping the spine straight and the head straight.
Raise your hands towards your face. Raise your elbows to shoulder level Put your thumbs on your ear holes. Block out all external noises
If your thumbs on your ears cause pain then close the ear canal by placing the thumb on the surface of the muscle near the ear canal.
Close the eyelids but the eyeball should be upwards.
Place the index finger and middle finger on the closed eyelids in such a way that pressure is applied to the entire eye but do not apply pressure on the eyeball.
Pull the eyelids down with the middle finger Push the part of the eyelid that is below the eyebrow up with the right finger.
Apply light pressure on both sides of the eye.
Let the pressure on the ears and eyes be equal.
Press both the nostrils with the tips of the ring fingers like pressure on the two nostrils will be same.
This will narrow the airways and initiate long, slow steady, rhythmic and subtle breathing.
Place the little fingers on the upper lips so that they can maintain the rhythm of breathing.
Remain in this position for as long as possible, fixing the gaze within.
Benefits of 'Shnmukhi mudra'
The senses turn inward and the rhythmic breathing stops the wandering of the mind.
creating inner peace and hearing the transcendental sound of the soul.
This mudra prepares the practitioner for the fifth stage of yoga called 'Pratyahara'.