Sūryanamaskāra (bowing down to Sūrya or the Sun-god) is practised by the Hindus not only as good exercise but also as a religious act.
It has to be done facing the rising sun in the early morning. There are twelve postures in it. Each posture has to be accompanied by the prescribed mantra containing one of the names of Sūrya like Mitra, Ravi, Sūrya, Bhānu and so on.
The tṛcākalpanamaskāra is one method in which after Om, a few mystic syllables and their combinations in twos and fours together with certain mantras are repeated with the twelve names.
Oṁ hrām udyannadya mitra mahaḥ hrām Oṁ mitrāya namaḥ ॥
This is the first mantra.