Samael Aun Weor from his lecture, A Transmutation Practice: Ham-Sah:
Sit down comfortably: the eastern way (cross-legged) or the western way (on a comfortable armchair). Relax your bodies as children do.
Inhale deeply, very slowly, and imagine that the creative energy rises through the spermatic channels up to the brain; mentally pronounce the mantra HAM like this: HAAAAAAAMM.
Exhale, short and quick, as you pronounce aloud the mantra SAH: SAAAAHH…
Undoubtedly, you inhale through the nose and exhale through the mouth. While inhaling, you “mantralize” the sacred syllabe HAM (mentally, since you are inhaling through the nose); but you can articulate the syllable SAH with sound while you exhale.
The marvelous symbol that in the East makes the chaotic waters of life fertile is Ham-Sah, the Third Logos. Usually, the sexual forces flow outwards from the inside in a centrifugal way and that is why there are nocturnal emissions; when you have a dream based on the Sexual Center, there occurs an emission, a loss of sacred sperm or spermatic liquor.
If one organizes one’s vital systems and instead of propitiating the centrifugal system, uses the centripetal system, that is, if one makes the sexual forces flow inwards from the outside through transmutation, then there are no emissions even if there may be erotic dreams.
One needs to organize one’s sexual forces if one wants to avoid emissions; such forces are closely linked with one’s nourishment, with the prana, with life – that is obvious. Therefore there is a profound relation between one’s sexual forces and one’s breathing, so that when both are duly combined and harmonized, they bring about fundamental changes in one’s physical and psychological anatomy.
To make the sexual energies “re-flow” inwards and upwards in a centripetal way is what matters; only thus is it possible to produce a specific change in the office and functions that the sexual creative force can fulfil. During Meditation one needs to imagine the creative energy in action, making the energy rise to the brain in a rhythmic, natural way by means of vocalising the mantra HAM-SAH, not forgetting to synchronize the inhalations and exhalations of air in perfect concentration, harmony and rhythm.
Let us make it clear that inhalation has to be deeper than exhalation simply because we need to make the creative energy flow inwards from the outside; that is, we need to make exhalation shorter than inhalation. With this practice there comes a moment when all the energy flows inwards and upwards. Clearly, the creative energy so organized – in a centripetal way – becomes an extraordinary instrument for the Essence, a means to awaken Consciousness.
[ ] Therefore, the creative energy combined with Meditation serves to awaken the Consciousness. Unquestionably, it draws the Consciousness out from the ego and into absorption in the Illuminating Void. Meditation combined with Tantra is tremendous. HAM-SAH is the key.
*Samael Aun Weor explains in other lectures that women should not practice transmutation exercises while menstruating.