"The learned master, initiates the disciple as per his qualities and his capabilities. If the disciple follows the instructions truly and dutifully, he attains perfection by it. A desireless condition is availed by perfection----which is possible in the Paravastha of Kriya. There are different kinds of Kriya acts, the able master does not teach them all at a time,
only the ones who get well versed in the previous acts are passed on to the next class of acts. If after the first initiation the tongue is not risen or elevated (above the palate) then the second class or "Vaisya" class is not promoted to, and further lessons are not taught. Yet, if whatever is known or learnt is dutifully practiced with a concentrated mind and pran, then the paravastha which is the fruit of such acts will surely be gained."
- Sri Sanyal Mahasaya from Spiritual Gita 18:45, English translation by Smt. Chandrakanta Agarwala
The practice of the technique of the Second Kriya is made possible with the method of piercing the tongue-knot by the technique of Khechari Mudra.
- Swami Satyananda Giri, Acharya Sanglap, book 2 page 67
After this comes the matter of Second Kriya. For this, Khechari Mudra is necessary.
- Swami Satyananda Giri, Acharya Sanglap, book 2 page 26