Regarding the revelation of the Longchen Nyingtik teachings, Tulku Thondup writes:
While Guru Rinpoche was visiting Tibet…he conferred the Longchen Nyingtik teachings on King Trisong Detsen, Khandro Yeshe Tsogyal, and Vairochana… He gave prophetic empowerments by saying that the teachings would be discovered by Jikmé Lingpa, an incarnation (tulku) of King Trisong Detsen.
So centuries later, when the prophetic empowerments of Guru Rinpoche ripened and the favorable circumstances came to fruition, the concealed Longchen Nyingtik teachings were accordingly awakened in the enlightened mind of Jikmé Lingpa as mind ter.
Jikmé Lingpa discovered the Longchen Nyingtik teachings as mind ter at the age of twenty-eight. Tulku Thondup writes:
In the evening of the twenty-fifth day of the tenth month of the Fire Ox year of the thirteenth Rabjung cycle (1757), Jikmé Lingpa went to bed with an unbearable devotion to Guru Rinpoche in his heart; a stream of tears of sadness continuously wet his face because he was not in Guru Rinpoche’s presence, and unceasing words of prayers kept singing in his breath.
Boudhanath Stupa
He remained in the depths of that meditation experience of clear luminosity for a long time. While being absorbed in that luminous clarity, he experienced flying a long distance through the sky while riding a white lion. He finally reached a circular path, which he thought to be the circumambulation path of Jarung Khashor, now known as Boudhanath Stupa, an important Buddhist monument of giant structure in Nepal.
In this vision, the wisdom dakinis gave Jikmé Lingpa a casket containing five yellow scrolls and seven crystal beads. One of the scrolls contained the prophetic guide of Longchen Nyingtik, called Nechang Thukkyi Drombu. At the instruction of a dakini, he ate the yellow scrolls and crystal beads, and all the words and meaning of the Longchen Nyingtik terma were awakened in his mind.
Jikmé Lingpa kept this terma secret for years, and he did not even transcribe the terma until he entered another retreat in which he had a series of visions of Longchen Rabjam. Tulku Thondup explains:
In the earth-hare year (1759) he started another three-year retreat, at Chimpu near Samye monastery. During that retreat, because he was inspired by three successive pure visions of Longchen Rabjam, and he was urged by repeated requests of dakinis, he transcribed his terma as the cycle of Longchen Nyingtik. On the tenth day of the sixth month (monkey month) of the monkey year (1764) he made his terma public for the first time by conferring the transmission of empowerment and the instructions upon fifteen disciples.
The Longchen Nyingtik terma consists of tantric sadhanas and teachings.
☝ Definitions:
terma - hidden teachings