Milarepa: Sexual Energy
"Bliss arises when the inner fire [tummo, Vital Heat] blazes throughout the body,
There is bliss when the winds of Roma and Kyangma [the two channels beside the spine] enter into the central channel [in the spine],
There is bliss when the bodhichitta [pure sexual energy] descends from above... and the translucent tigle [sexual energy] pervades from below.
When the white and red [male and female essences] unite in the middle [at the heart],
And the joy of a leakless body satiates one,
The whole body is suffused with undefiled rapture.
Sixfold is the bliss of the secret yogas." - The Song of the Snow Ranges