In the Vedas of yore there is clearly defined an ancient tantric practice, known as bhuta shuddhi. Bhuta shuddhi literally means 'cleansing or refining the physical elements', however, apart from this, its actual meaning should be considered as 'refining the underlying consciousness related to the elements'.
We all know that matter is composed of five elements: earth, water, fire, air and ether. The different proportions, quintuplication, permutation and combinations of these are responsible for the formation of matter in its gross form. In the same way, the human body is also composed of these five elements.
If you can develop a process to purify and separate these elements, you can return to the source of matter and discover the potential energy or subtle form behind the gross form. Just as a scientist breaks down matter into elements and finally arrives at the subtlest form, which is energy, similarly, the tantric or yogi purifies his gross body elements and finally realises the ultimate source of matter which is pure consciousness.
First think of kundalini rising from mooladhara chakra (sacral plexus) up to sahasrara chakra, along the sushumna canal. The practitioner is to meditate on the mantra Hamsa and consider himself united with Brahman (supreme consciousness). Then bring your awareness from the legs to the knees in the form of a square yantra. Consider this square to be composed of the earth tattwa (element) which is a golden colour and is represented by the bija mantra Lam.
Next bring your awareness to the portion below the navel. Imagine there the form of a semi-moon with two lotuses at each end. This is surrounded by a circle of water, white in colour and represented by the bija mantra Vam.
Then bring your awareness from the navel to the heart and imagine there a yantra of triangular shape, with swastika marks on each of its three sides. This is the fire tattwa; it is red in colour and is represented by the bija mantra Ram.
Next bring your awareness from the heart to the centre of the eyebrows, and imagine there the form of six dots in a circular shape. These are symbolic of the air tattwa, which is of smoky hue and is represented by the bija mantra Yam.
Then bring your awareness from the region of the eyebrows to the crown of the head and imagine there the akasha mandalam or the region of ether, beautiful and clear, with Ham as its bija mantra. Thus ponder on the earth principle dissolving into water, its cause. Then water dissolving into fire, its cause. Then fire dissolving into air, its cause, and air dissolving into ether, its cause.
Now imagine akasha dissolving into ahamkara (ego), its cause. Then ahamkara dissolving into maha tattwa (the great principle). And maha tattwa dissolving into prakriti, prakriti into the supreme Self. Then consider yourself as the highest knowledge, pure and absolute.
Imagine now that the 'papa purusha' or sinful man; who is about the size of your thumb, is situated at the left of your abdomen. His form is grotesque, black as coal, with fiery eyes, big teeth and a large belly. In his hands he holds axes and shields. Inhale air through the left nostril, mentally repeating the bija mantra Vam for water. Perform kumbhaka and imagine that you are purifying the sinful man. While doing kumbhaka, repeat Ram, the bija of fire, and think of the sinful man being burnt to ashes. Then exhale the ashes of the sinful man through the right nostril. Next meditate on the water tattwa again, repeating the bija mantra Vam, and imagine the ashes of the sinful man being rolled into a ball with nectar from the moon.
Think steadily of this ball being turned into a golden egg, while meditating on the earth tattwa, represented by the bija mantra Lam.
Repeat the bija mantra Ham, ether tattwa, and imagine yourself as an ideal being pure and clear. Create the elements afresh in the reverse order from Brahman the absolute, then ether, air, fire, water and earth and locate them in their respective positions, in the forms described earlier, represented by their bija mantras. Then repeating the mantra Soham, separate the jivatma or individual soul from paramatma or the cosmic soul and locate the jivatma in the heart region. Think also that the kundalini has returned to mooladhara via sushumna, piercing the chakras. Next meditate on Prana Shakti, the vital force, seated on a red lotus in a vast red ocean. She has six hands which are holding the trident, bow of sugarcane, noose, goad, five arrows and a skull filled with blood. She has three eyes, highly decorated breasts and her body is the colour of the rising sun. Thus meditating, one should apply ashes on the body.
Ideally bhuta shuddhi should be practised three times a day; morning, midday and at dusk. However, the number of times can be reduced according to one's lifestyle. Practice of bhuta shuddhi is not restricted to a particular sect or cult; anyone can practise it.
These days there is a tendency for many to plunge into vama marga, because they think it is a philosophy synonymous with free lifestyle and living. However, I would like to point out that this practice and other forms of purification, such as manas shuddhi, prana shuddhi, deva shuddhi, mantra shuddhi, should become a daily discipline before taking to the practices of vama marga or any other marga, Tantra is very clear on this. Vama marga is only for those who have control over their minds.
Tantric practices start with bhuta shuddhi, which begins from the moment one wakes up. You are taught the daily disciplines of bathing, brushing of teeth, etc., from a very early age so, you do them without a second thought. But if, for some reason, you are unable to complete them on any day, you feel uncomfortable and ill at ease. In the same way, this practice too should become a part of your daily routine. Perhaps it should have greater importance, because it is not only conducive to physical hygiene but also to mental hygiene. That is precisely the reason the shastras and scriptures stress the fact that only after the discipline of bhuta shuddhi is perfected, is atma shuddhi or purification of consciousness possible.