Dudjom Lingpa &
Heart of Great Perfection
Although I practiced in that way, when I encountered even a minor issue, I would lose my own grounding in the nature of existence and revert to ordinary states. For example, when I was alone and naked in the wilderness, if I were to become frightened when various ferocious animals and savages let out terrifying roars, I would be no different than an ordinary person. In that case, there would be no way I could be liberated in the intermediate period by way of such meditation. But with heartfelt faith and reverence I prayed to my guru, the Lake-Born Vajra, “Please grant me right now practical instructions for handling such circumstances!” Falling asleep with immense devotion, in a dream I had a vision of Orgyen Dorjé Drolö* appearing from an expanse of blazing fire and light, and he chanted the lyrics of this Hūṃ song: 
*Orgyen Dorjé Drolö refers to Guru Rinpoche, Padmasambhava
Hūṃ Hūṃ! Supreme being, Vajra of Pristine Awareness,
Hūṃ Hūṃ! do you understand the common thread of the three realms of saṃsāra
Hūṃ Hūṃ! as dualistic grasping at the apprehender and the apprehended?
Hūṃ Hūṃ! Do you understand both the object and the subject
Hūṃ Hūṃ! as two thoughts?
Hūṃ Hūṃ! Do you understand the joys and sorrows of this life and future lives
Hūṃ Hūṃ! as delusive experiences?
Hūṃ Hūṃ! Do you understand daytime appearances, nighttime appearances, the physical world, and its sentient inhabitants
Hūṃ Hūṃ! as experiences of light and dark?
Hūṃ Hūṃ! Do you understand the joys, sorrows, environment, and friends of this life
Hūṃ Hūṃ! as dream experiences and delusive appearances,
Hūṃ Hūṃ! and know that they are equally unreal?
Hūṃ Hūṃ! As vast as the physical world and its sentient inhabitants are,
Hūṃ Hūṃ! they do not extend beyond the expanse of space.
Hūṃ Hūṃ! Although space has no periphery or center,
Hūṃ Hūṃ! it does not extend beyond the expanse of pristine awareness.
Hūṃ Hūṃ! Buddhafields and excellent buddhas
Hūṃ Hūṃ! are the face of your own ground, the nature of existence.
Hūṃ Hūṃ! Do not mistake the buddhas as being autonomous.
Hūṃ Hūṃ! I shall cut off the errors of the māras above.
Hūṃ Hūṃ! Enemies, demons, bad companions, and your surroundings
Hūṃ Hūṃ! are delusive experiences of conceptual, dualistic grasping.
Hūṃ Hūṃ! Do not regard them as anything other than reification.
Hūṃ Hūṃ! I shall destroy the errors of the māras below.
Hūṃ Hūṃ! Daytime and dream appearances
Hūṃ Hūṃ! are reified and clung to as names and things. 
Hūṃ Hūṃ! Even though you know emptiness for yourself,
Hūṃ Hūṃ! do you understand thoughts as aspects of your own nature?
Hūṃ Hūṃ! While you understand all of saṃsāra and nirvāṇa
Hūṃ Hūṃ! as the primordial expanse of the absolute space of the ground,
Hūṃ Hūṃ! do you understand them as nondual displays [of pristine awareness]?
Hūṃ Hūṃ! Appearances of these creative expressions slip into the essential nature of uniform pervasiveness,
Hūṃ Hūṃ! releasing themselves into that expanse.
Hūṃ Hūṃ! Do you understand that there is no practice of meditation?
Hūṃ Hūṃ! Inwardly there is the bondage of grasping at the “I.”
Hūṃ Hūṃ! Outwardly there is grasping and clinging to objects.
Hūṃ Hūṃ! Meditation in between is immaterial.
Hūṃ Hūṃ! Do you understand that the gateways of
Hūṃ Hūṃ! outer and inner conditions obscure the face
Hūṃ Hūṃ! of the Great Perfection of saṃsāra and nirvāṇa?
Hūṃ Hūṃ! First, by investigating, understanding will come.
Hūṃ Hūṃ! Next, by meditating, experiences will arise.
Hūṃ Hūṃ! Finally, by resting, realization will come.
Hūṃ Hūṃ! Once realization has occurred, it is nondual with simultaneous liberation.
Hūṃ Hūṃ! Objects and subjects together
Hūṃ Hūṃ! are awakened in the mother’s space of the great expanse.
Hūṃ Hūṃ! My emanations and I
Hūṃ Hūṃ! have never been separated.
Hūṃ Hūṃ! Their essential nature is the illusion of my own creative expressions.
Hūṃ Hūṃ! Like the dissolution of the apparitions of an illusionist,
Hūṃ Hūṃ! they are nondual in absolute space. Phaṭ Phaṭ!
With those words he became nondual with me, and an experience arose of my great appearances pervading all of saṃsāra and nirvāṇa. From that time onward,  due to this sign, I knew that these were pith instructions for collapsing the false cave of appearances.
To expand on this just a little, (1) seek out the source of names, (2) destroy grasping at the permanence of things, and (3) collapse the false cave, which is primordially liberated within your own mindstream, by knowing and realizing all of saṃsāra and nirvāṇa.
1. Seek Out the Source of Names
By investigating and analyzing the tenacious grasping of saying the name “I” and grasping at the thought “I am,” you find that the basis of designation of everything—including the flesh, blood, and bones, throughout the exterior and interior of the body, and from the crown of the head down to the soles of the feet—is nonobjective and empty. Then continue to expose the error by also seeking out each of the specific names of the head, feet, arms, joints, and so on. As for the way to investigate all manners of establishing names and conventions in the external environment, by seeking out the name house, for example, in terms of its exterior, interior, upper, and lower areas, and its clay, stones, and so on, it disappears by itself. Earth becomes pottery; and the names of the upper and lower sections of stones, the tops and bottoms of trees, and so forth naturally disappear from where they are, and through transformation and modification they become water mills, stoves, pillars, and beams. Water becomes tea, fire becomes the flame of a butter lamp, air becomes a gust in a bellows, and so on. Reveal the fallacy in each of these cases that the bases of designation of such transformations, cessations, and disappearances  cannot be ascertained.
Translation by Alan Wallace