[After an extensive and detailed description of Meditation practices to harness and control the vital energies, the Panchen Lama wrote]:
When the practice has developed stability and you have arrived at the point where the knots constricting the heart chakra are ready to be released, take up the practice of karmamudra ["action seal"] with a qualified sexual consort, with you being the relier and the consort being the relied-upon, until the energies that support the final semblant clear light arise in the actual form of Heruka. [Nagarjuna's] The Five Stages describes the experience thus:
The illusion-like samadhi
Perceives everything in that way.
The meaning of this passage is that the illusory samadhi is taken to complete fulfillment.
The illustrious Naropa said to Marpa Lotsawa,
Day and night appearances manifest as illusory forms;
This is the instruction known as "the illusory body."
Have you reversed all grasping at appearances, O Lotsawa?
The practitioner takes the illusory Yoga to fulfillment, and eventually perceives the signs of the eradication of all spiritual distortions [egos or aggregates], together with their seeds. He or she relies on the inner conditions of the energy yogas and the outer conditions of a sexual consort, and this causes the inner and outer signs of enlightenment to manifest. This is the experience of the actual clear light. Jey Naropa sand to Marpa Lotsawa,
In the space between sleep and dreams
Is unknowing, in nature the Dharmakaya.
It is to be drawn into one's experience
As inexpressible, uncontrived emptiness.
Thereafter, whatever appears arises as bliss.
This is the unfabricated primordial nature of being
And is called "the clear light instruction."
Have you fathomed this unborn mind, O Lotsawa?
From the uncontaminated energy and Consciousness that support this mind of actual clear light arises the vajra body of great union, on the basis of which the resultant state of full buddhahood in the form of Vajradhara endowed with the seven excellent qualities is acheived.