Kriya Yoga is not alien to Vaishnavism. Jagatguru referred Kriya Yoga (Pranayama) when expounding Bhagavadgita to Arjuna. Bhagavadgita verse 4.29 talks about Pranayama which is part of Kriya Yoga.
apāne juhvati prāṇaḿ
prāṇe ’pānaḿ tathāpare
prāṇāpāna-gatī ruddhvā
prāṇāyāma-parāyaṇāḥ
apare
niyatāhārāḥ
prāṇān prāṇeṣu juhvati
Still others, who are inclined to the process of breath restraint to
remain in trance, practice by offering the movement of the outgoing
breath into the incoming, and the incoming breath into the outgoing,
and thus at last remain in trance, stopping all breathing. Others,
curtailing the eating process, offer the outgoing breath into itself
as a sacrifice.
The procedure of Kriya Yoga is explained in detail in chapters 26 and 28, 29 of Vasudeva Mahatmya- Vaishnava Khanda of Skanda Purana.
Sri Narayana Rishi explains the Kriya Yoga to Narada as follows:
Sri Näräyana said:
I. After sipping water and practising breath-control (with Oh bhür
etc.) and then with a composed mind, one should pay obeisance to one's
desired deities, and proclaim the time (tithi etc.) and place (of
worship).
2 After taking the solemn vow (the formal Sankalpa), "I shall perform
the worship of Väsudeva for the accomplishment of Ekänta Dharma," one
should then perform the procedural Nyäsa (i.e. assignment of the
various parts of the body to deities accompanied with prayers or
Mantras and corresponding gesticulations).
After this, proper mantras should be recited based on Varna by imagining the resplendent Krishna and Radha.
After sprinkling the articles of worship and one's own person with the water from the (worshiped) pitcher and after worshiping the conch
and the bell, one should perform the purification of the bhütas (i.e.
elements constituting the body).
After burning the (internal) sinful body with internal fire and wind, one remaining stable (in one's posture), should reflect upon the
identity of one's pure self with Brahman.
Then performing breath-control, one should, with concentrated mind, meditate upon Lord of the form of imperishable Brahman in one's
heart.
The lotus (i.e. the Yogic plexus) at the navel is in a drooping position like the flower of Kadali (plantain tree). Reflecting upon
the vital wind called Apäna, one should bring about its union with
the vital wind called Präna.
After bringing it in the hollow stalk of the lotus (the internal
path through which life breath proceeds upwards, the path of
Kundalini), one should pull in the upward direction that 'lotus'
along with that (breath). Making a loud sound it goes to the 'heart'
(known as hrtkamala). It fully blossoms there shiningly expanding in
the cavity of the heart.
In the mass of light (permeating that 'sky') one should meditate upon quiescent Sri Krishna, the Lord of Rädhikä who is the most
beautiful and outstanding, by his surpassing superior refulgence.
This chapter describes in detail forms of Radha and Krishna on whom one should mediate.
After worshiping mentally, now devotee should worship Idol of Vishnu with Bhakti. This is similar to normal pooja.
After worshiping him mentally with various articles (and services) of worship, the devotee should invoke him and establish (infuse) him
in the idol of Vishnu by Sthäpana Mudrä (i.e. a certain position of
fingers practiced in worship to indicate that the deity invoked is
established in the idol).
Then he should invoke the deities constituting him (i.e. his subordinate deities) by their respective separate Mantras or by their
names (which itself is a) mantra, and then should establish them well.
He should ring (or play upon) some musical instrument like the bell and others and should make a clapping sound. Presuming that the
deity has got up from sleep, he should brush (i.e. imagine to brush)
the teeth.
He should give water mixed with Syämäka (a rice-like corn), Visnukränta (a plant like Clitoria terntea), Dürvä grass and a lotus
as Pädya (water for washing the feet) to the Lord. Then in the water
meant for sipping as Arghya, he should put sandalpaste, rice-grains
with unbroken ends, flowers, ends of Darbha grass, gingelly seeds,
mustard seeds, barley seeds. Dürvä grass should be put after filling
the vessel for Arghya with water.
After that idol should be smeared with oil, offered Tulsi leaves and some Prasada, which is described in this chapter. After completing the above procedure one should mediate on Radha Krisha by invoking them into his heart.
- After meditating on the rest and after taking (permission) given by him reverently by head, one should establish as before the invoked
Rädhä and Krsna in the lotus of his heart and should send away all the
Anga-devas to their respective places.
This chapter further explains various Mantras of Vishnu on which a devotee should meditate.
Sri Narayana Rshi also explains Astanga Yoga, Pranayama and Kundalini Yoga (raising Kundalini through various Chakras by meditating of Keshava) in this chapter.
