The Kriya meditation system of the Himalayan adept (siddha) lineages utilizes three methods that are combined using stepwise micro-postural movements and mental strikes (mudrā). These three parts include: imbibing light by sun gazing and open-eye meditation (śāmbhavī mudrā) on the sun with internal focus on the mid-point of the eyebrows; perfected internal breathing (ujjāyī) in particular circuits (nādi); and chanting or rumination on the primordial Oṃ sound. Oxygenation is increased in the body by synchronizing the internal breath with rumination on Oṃ.
Breathing and quieting the mind become part of the same effort. The best results are obtained when the Oṃ sound is repeated at about 432Hz or 528Hz. Sun gazing methods and the related mudrā, prānāyāma, and yoga-vinyāsa techniques are collectively known as surya-kriyā, and are practiced in tandem with the sunrise. Open-eye meditation (śāmbhavī mudrā) when the sun is above 15° is practised with great care to avoid any UV damage. All of these special techniques have been systematized and revealed by Tryambaknath (popularly known as Mahavatar-babaji) and can only be undertaken when learnt properly from authentic meditation lineages.
In summary, the techniques of kriyāyoga and its family of related meditation practices use specific ujjāyī prānāyāma techniques that recharge the blood and the cerebrospinal fluid with prāna (vital energy) infused in the correct nādī circuit (energy pathway related to nerves, blood vessels etc.). The group of techniques applies particular mudrā (postures to retain prāna) when the internal mental rumination of the primordial sound syllable is synchronized with the perception of prāna.
Correct practice of kriyā-prānāyāma infuses prāna into the nādī to attain a momentum of habitual engrossment (samāpatti) ultimately bringing about the aftereffect saturation (parāvasthā). The meditator further undertakes subtle mental kriyā exercises during this aftereffect poise. This kriyā-based approach is distinct from other prānāyāma-based meditation practices. Moreover this synchronized practice using breath, light, sound, and subtle feelings (subtle movement sensations) constitutes an internal mindful action that brings about poise and alacrity. This approach is distinct from sitting meditation where one observes and releases subtle desires by minutely watching the breath while bearing through distractions to repose in silence.