It is mentioned in Lamrim Yeshe Nyingpo, The Gradual Path of the Wisdom Essence, by Guru Rinpoche, that there are four levels of heart-practice or guru sadhana: the outer is Barché Künsel, the inner is Sampa Lhündrup, the secret is Tsokyé Nyingtik, and the innermost secret is Dorjé Draktsal. The terma or treasure root text states:
Externally, in order to dispel all obstacles, ༔
by means of Nangsi Zilnön, the trikāya Padmākara, ༔
with the twelve manifestations of vidyādhara power-wielders, ༔
practice the approach in the general and special manners. ༔
Internally, in order to spontaneously accomplish supreme and common wishes, ༔
by means of Wish-fulfilling Great Bliss, Padmasambhava, ༔
together with the thirteen gurus, ༔
make the full approach of means and liberation, development and completion. ༔
Secretly, by means of indivisible space and awareness ༔
manifest in the mudra form as Padma Vajradhara, ༔
all the three roots condensed, and through the essence yoga, ༔
gain accomplishment of the unchanging coemergent wisdom. ༔
Most secretly, by means of Vidyādhara Dorjé Drakpo Tsel, ༔Lamrim Yeshe Nyingpo, trans. Erik Pema Kunsang, ed. Marcia Dechen Wangmo. Rangjung Yeshe Publications: Hong Kong, 2016.
the embodiment of all sugatas, the deity who has totally perfected all herukas, ༔
and through the nyegyü practice, the great accomplishment, ༔
realize the ultimate kāyas and wisdoms. ༔
Jamgön Kongtrul, in his commentary on the above-quoted root verses of Lamrim Yeshé Nyingpo, explains the significance of Guru Tsokyé Nyingtik as follows:
Secretly, the means is the indivisible unity of primordially pure space and spontaneously present awareness, which itself is the basic nature of your own mind and all phenomena. The meaning of this is manifest in mudra form as the great Padma Vajradhara, Tsokyé Dorjé Chang, the symbol, who is all Three Roots condensed into one. He is the self-existing wheel of great bliss, and through his profound path of the essence yoga of undivided development and completion, you reach ‘accomplishment’ of unchanging co-emergent wisdom….Light of Wisdom, Vol. II, trans. Erik Pema Kunsang. Rangjung Yeshe Publications: Hong Kong, 1998, pp. 65-66.
In 1848, at the age of twenty-eight, when Jamyang Khyentsé Wangpo was in the vicinity of Gegyel on his way to central Tibet, he performed a feast offering on the auspicious occasion of Guru Rinpoche’s birthday, in the monkey month of the earth monkey year, which marks the year that Guru Rinpoche was born. His experience blazed forth. He then went outside and found a beautiful cave whose entrance faced the southwest. Curious, Khyentse Wangpo entered the cave and was immediately filled with joy. After practicing Guru Yoga there, he briefly fell asleep and was suddenly awoken by a loud noise. In the space in front of him, Guru Rinpoche appeared as the Guru of Zahor surrounded by a vast retinue. Guru Rinpoche blessed Khyentsé Wangpo and dissolved into his heart. As a result of this, the root practice of Guru Tsokyé Nyingtik (Lake Born Guru’s Heart Essence) appeared clearly before Khyentsé Wangpo’s mind, and he put the activity manual into writing right then and there.
Jamyang Khyentsé Wangpo then continued his journey and arrived at Samyé monastery on the Full Moon of the ninth month. He made vast offerings to the treasure statue of Guru Tsokyé Dorjé (Lake-Born Vajra Guru) revealed by the Great Tertön Nyangrel Nyingma Özer. As he was practicing, he had a vision of the statue becoming alive and granting him the empowerment and further instructions, finally dissolving into his heart. The cycle’s auxiliary teachings also vividly arose in his realized experience, and he placed them under a seal of secrecy. The following winter, upon his fervent request, Chokgyur Dechen Lingpa received the Guru Tsokyé Nyingtik empowerment and instructions from Khyentsé Wangpo. That night, Chokgyur Dechen Lingpa had an extraordinary dream in which Guru Rinpoche empowered him as the custodian of these teachings. Through these blessings, Chokgyur Lingpa also revealed further related treasures from Sengchen Namdrak. Later, once he had completed the approach and accomplishment for the practice, at the occasion of a feast gathering on the tenth day of the month, his realization manifested as he hung up his damaru and bell in the air so that all those around could see. With these extraordinary signs of blessings, the Guru Tsokyé Nyingtik became the third of the four guru sadhanas common to the two great tertöns.