Urdhvaredham Viroopaaksham Viswaroopayay Namaha'-Narayna Suktham. At some point of time when Yoga is being practiced,when a practitioner is advancing,he shall have sexually stimulating visions,especially during Sakthi Upasna and he can advance only if he overcomes the stimulation and direct the flow upwards.
The number of people who were blessed, as of now, is 12. I can only say that it is the result of their faith and meticulous following of the procedures. The ultimate prayer one must follow is that wants nothing in return. This is what is most useful for what we need keeps on changing and the more one gets,sadder he becomes later because of what he asked for. So God knows what is good for you and you need not ask for it for a mother knows what is needed for the child.
There is Narayana Tantra which deals with Tantra. Even in this only basic aspect is referred. There is no elaborate description of Tantra Sri Vaishnavam. One finds elaborate description of Tantra aspects of Hinduism in Saivite texts, Shiva, Shakti,Ganapati,Subrahmanya. But this aspect is noticeably absent in Sri Vaishnavam.
One is Bhakthi tinged with Reason and Intellectual approach. Another is total emotional immersion in the Love of God. And example of an intellectual bhakti may be discerned in Kalidas's first sloka of Raghuvamsa , which set about describing the Dynasty of Lord Rama. Curiously the work that is about to talk about Lord Hari,Vishnu , begins with a Sloka on Lord Shiva and Parvathi. This is the sloka. The genius of Kalidasa lies in that this poem is open for Twenty Five meanings!
The Modifications of the Mind, Chitta Vrutti' -when it falls still, the Mind Becomes still and this is real Silence. This is what is required for a practitioner of Yoga and this is the goal of Yoga. An indication how this is taken seriously can be seen in Ghoshala, a village near Manali.