Of the ten root and branch winds, the most important for Secret Mantra meditation is the life-supporting wind. This wind has three levels: gross, subtle, and very subtle. It is the very subtle wind that travels from life to life, supporting the very subtle mind. This very subtle wind and the very subtle mind never separate, which is why the very subtle wind is called ‘indestructible’. The indestructible wind is located in a tiny vacuole inside the central channel at the centre of the heart channel wheel. It is enclosed in the very centre of a small sphere, the indestructible drop, which is formed by the very subtle white and red drops.

      We need an intimate knowledge of the life-supporting wind because it is the object of meditation of completion stage practices such as vajra recitation. This practice, which is done inside the heart channel wheel, is a method for loosening the knots at the heart. It is essential to loosen these knots if our Mahamudra practice is to be successful.

      THE CONTAINED DROPS

      There are two types of drop in the body: white drops and red drops. The former are the pure essence of the white seminal fluid and the latter are the pure essence of the blood. Both have gross and subtle forms. The white and red drops that flow outside the central channel are gross drops. The central channel contains both gross and subtle drops.

      The principal seat of the white drop (also known as ‘white bodhichitta’) is the crown channel wheel, and it is from here that the white seminal fluid originates. The principal seat of the red drop (also known as ‘red bodhichitta’) is the navel channel wheel, and it is from here that the blood originates. The red drop at the navel is also the foundation of the warmth of the body and the basis for attaining inner fire, or tummo, realizations. When the drops melt and flow through the channels, they give rise to an experience of bliss.

      For practitioners of Secret Mantra, the channels, winds, and drops are the bases for attaining spontaneous great bliss. Beings whose bodies are not endowed with these three have no opportunity to practise Highest Yoga Tantra. Thus, the human body is the perfect vehicle for Secret Mantra meditations, which is why it is regarded as so precious. In general, to practise Highest Yoga Tantra one must be a womb-born human being possessing six elements: earth, water, fire, wind, channels, and drops; or, according to another way of listing them, bone, marrow, and white drops obtained from the father; and flesh, skin, and blood obtained from the mother.

      THE REASON WHY THE WINDS CAN ENTER THE CENTRAL CHANNEL BY PENETRATING THE PRECISE POINTS THROUGH THESE DOORS

      To bring the winds into the central channel, we must practise meditations that focus our concentration at any of the ten doors mentioned above. The practices of Heruka, Guhyasamaja, Vajrayogini, and so forth contain different technical methods for penetrating these points. In some, concentration is focused at the centre of the heart channel wheel, in others at the centre of the navel channel wheel, and in others at the upper and lower ends of the central channel. According to the system set forth in the Six Yogas of Naropa, the winds enter the central channel through the door of the navel channel wheel. This is also the door used by the present system of Mahamudra meditation. When we gain confidence that the winds can enter the central channel through the navel channel wheel, we will also know how they can enter through the other nine doors.

      As mentioned before, there are sixty-four spokes of the navel channel wheel, or emanation wheel. The central, right, and left channels ascend through the hub of this channel wheel, the right and left each coiling around once to form the twofold knot there. In the centre of this knot, inside the central channel, there is a small vacuole similar to a small air bubble. This vacuole is the point to penetrate when meditating on inner fire, or tummo. When performing inner fire meditation, we focus our concentration on this vacuole and clearly visualize a letter short-AH inside it. Concentrating single-pointedly on this short-AH is known as ‘penetrating the precise point of the navel channel wheel of the vajra body’. If we meditate on our mind as indistinguishably mixed with the short-AH, and practise this meditation again and again with strong and steady concentration, we will be successful in bringing the winds into the central channel at this point.

      Why will this meditation cause the winds to enter the central channel? The reason is that mounted winds and the minds that mount them are inseparable, just like a body and its shadow, and so if the mind gathers within a vacuole inside the central channel, the winds must also gather there. Strong and consistent practice of this meditation will cause the central channel gradually to open. This explains how the winds may be brought into the central channel through the navel channel wheel, and in the same way we can understand how the winds may enter the central channel through any of the other nine doors.

      It is most important to be very accurate when penetrating these points, identifying their exact locations in the very centre of the hub of the channel wheels inside the central channel. Sometimes, instead of the short-AH, other letters can be visualized within the vacuoles. For example, in some meditations a RAM is visualized at the navel and in others a HUM or a tiny drop is visualized at the heart.

      A quick method for gathering the winds within the central channel is to practise penetrating the precise points while holding the vase breath, which will be explained below. Once the winds have entered the central channel, spontaneous great bliss can be generated without difficulty. The winds that flow inside the central channel are extremely beneficial and conducive to realizations. Normally, because our winds are moving in the right and left channels, they give rise to gross conceptual thoughts that interfere with single-pointed concentration and cause our concentration to become scattered, but when the winds are in the central channel they do not support such conceptual thoughts. All gross conceptual distractions are pacified and our meditative concentration is powerful and penetrating. Thus, we are able to hold any object we choose with unmoving concentration.

      AN EXPLANATION OF THEIR DIFFERENT FUNCTIONS

      In general, any wind may be brought into the central channel through penetrating any of the ten doors. However, during completion stage, penetrating each channel wheel performs a different function. Penetrating the crown channel wheel increases the white drops, penetrating the throat channel wheel makes dream practices very powerful, penetrating the heart channel wheel enables us to maintain the appearance of clear light, penetrating the navel channel wheel increases inner fire, penetrating the channel wheel of the secret place induces an experience of strong bliss, and penetrating the channel wheel at the tip of the sex organ enhances the experience of strong bliss and induces a quick, deep, and long sleep.

      Why is the last ability important? Secret Mantra meditators wishing to use sleep as a spiritual path need to fall asleep quickly and sleep for an extended period of time. To achieve this, they penetrate the precise point of the sex organ channel wheel just before falling asleep, and then train in completion stage practices during their protracted sleep. However, if we cannot practise completion stage while awake, we will not be able to practise it during sleep. Practising completion stage during sleep prepares us to be able to practise it during the death process, which is the most important time to practise.

      At death we need to be able to practise three special methods: bringing the clear light of death into the path to the Truth Body, bringing the intermediate state into the path to the Enjoyment Body, and bringing rebirth into the path to the Emanation Body. To be successful in these, we need to prepare beforehand by training in the completion stage practices that bring the clear light of sleep into the path to the Truth Body, dreaming into the path to the Enjoyment Body, and waking into the path to the Emanation Body. Therefore, the Secret Mantra meditator strives to remain for a long time with the experience of the clear light of sleep so as to practise these methods.

      Ordinary people have a very brief experience of the clear light of sleep, but they are unable to recognize this experience or to maintain it for long periods. Nevertheless, everyone has the potential to develop the experience of the clear light and to use this experience as the spiritual path.

      Finally, it should be noted that it is not only when falling asleep that we should penetrate the precise