Let the Void be your cauldron; let Nature be your furnace; for your primary ingredient, take stillness; for your reagent; use quietude; for mercury, take your vital essence; for lead, use your vital energy; for water, use restraint; for fire, take meditation.
[Union of the Triple Equation]
Triple Equation of essence, energy and spirit unites to form the Golden Elixir of immortality during deep meditation. According to Master Chao Pi Chen the generative force changes into vitality when the body is still; vitality changes into spirit when the heart is unstirred; and spirit returns to nothingnessb because of immutable thought. The Elixir Field (Dantien) under the navel is where the genrative force [essence] is sublimated into vitality [energy]; the middle Elixir Field in the solar plexus (Middle Dantien) is where vitality is sublimated into spirit; and the upper Elixir Field in the brain (Upper Dantien) is where spirit is sublimated for its flight into space.
“When the mind is stilled, the spirit radiates a brilliance that illuminates all the great mysteries of the universe”. Chao Pi Chen
Reference: The Tao of Health, Sex & Longevity by Daniel P. Reid