Three parts:
Essential point of the body posture
Essential point of the visualization
How to do the medium training using spheres
1: Essential Point of the Body Posture
The essential point of the body posture is the seven-point body posture. This has already been explained earlier, but to summarize the are legs crossed, hand in equipoise, backbone straight, stomach pressed in, neck bent, tongue joining the upper plate, and shoulders lifted back.
2: Essential Point of the Visualization
The essential point of the visualization is to remember the explanation of the hollow interior of the Sambhogakaya and the Nirmanakaya visualizations taught previously. (Dharmakaya Hollow Interior Practice is not used here.)
3: How to do the medium training using spheres
Visualize a white sphere sixteen finger-widths from your right nostril floating in space and a red sphere sixteen finger-widths from your left nostril floating in space. A white sphere floating on the right, a red sphere floating on the left. White and red represent the nature of method and wisdom.
Next, inhale through both nostrils. At that time, both red and white spheres travel in through the left and right nostrils and down the red and white channels. Keep inhaling as much as you can as the spheres go down the two channels. At the junction of the three channels, the two spheres combine and mix into one single sphere. This sphere is white with red hues/luster. This sphere dwells at the junction of the three channels. Now hold the breath for as long as you can and concentrate on this single sphere at the junction of the channels.
When you exhale, imagine the white with a red luster single sphere rises up through the central channel and comes out the crown of the head and spreads back into two spheres - one red and one white back at their original positions sixteen finger-widths from your nostrils.
In the morning, we should do seven or twenty-one cycles (all three) during a single meditation session. One day we can work up to doing four or six meditation sessions a day. But in this busy life, we should aim for what we can even if it’s just one, two, or three practice sessions a day. We should make an effort to practice like this for three days.
At the end of a practice session (after seven or twenty-one cycles), visualize the spheres dissolve into the heart. Rest in the empty luminosity of the heart that is without reference point for as long as you can.
Summary:
These three trainings of the syllables, spheres, and winds are like making irrigation channels for water to enter the farmer’s fields before it is watered. That is why these trainings are important.
The benefit of these three trainings are that all gross and subtle level conceptual thoughts are stopped and the mind functions properly without diffusion. The mind does not move away from its object of visualization. This is why Tummo practice is more important than understanding how to practice. You need to train in this way, and when you become an expert in this practice the main practice of Tummo can be practiced properly. These are the secret methods of practice to reduce our suffering and realize happiness. It is not easy to understand. Nor do we need to fully understand it before we practice. But through practice we can come to understand. If you wait for understanding to practice, you might be waiting a very long time.