The teaching of Dzogpachenpo was first given in the pure realm
of Akanishtha, where the teacher Samantabhadra, in Sambhogakaya
form, communicates the teaching directly by means of his wisdom
mind to disciples who are not different from him in any way-sugatas
and bodhisattvas, male and female.
Now, in this world of ours, the first to spread the teaching of
Dzogpachenpo was the Nirmanakaya emanation Garab Dorje. Dates given
for Garab Dorje put his birth in the year 536BC; by comparison, one
popular date for the passing away of Lord Buddha, from the
Theravada traditon of Sri Lanka, is 543BC. From the glorious Lord
of Secrets, Vajrapani, or it is often said Vajrasattva, Garab Dorje
received, in an instant and all together, the empowerments, as well
as the tantras, agamas, and upadeshas, of Dzogpachenpo. Then in the
north of the western land of Oddiyana, on the rugged mountain-peak
of uryaprakasha, the vidyadhara Garab Dorje,along with the
wisdom dakinis, gathered and complied all the tantras in existence,
both those that were known and those that were unknown. Together
they divided the 20,000 tantras which bore the name of Dzogpachenpo
into ʻshlokasʼ or verses, and classifi ed them into 6,400,000
verses. Garab Dorjeʼs disciple, Manjushrimitra,
then divided these 6,400,000 verses of Dzogpachenpo into three
categories:
the outer category of mind-Semde,
the inner category of space-longde, and
the secret category of pith instructions-Mengakde.
The first four masters in the lineage left this world in a
characteristic way. At the end of his life, the first human
Dzogchen master Garab Dorje disappeared into a sphere of rainbow
light, leaving his disciple Manjushrimitra his last testament
ʻHitting the Essence in Three Wordsʼ, Tsik Sum Ne Dek. When
Manjushrimitra departed from this world, vanishing in a cloud of
light, he gave his laste testament to his disciple Shri Singha,
entitled ʻSix Experiences of Meditationʼ, Gom Nyam
Drukpa. When Shri Singha passed away and dissolved into a body of
light, he bestowed his testament ʻSeven Nailsʼ, Zerbu Dun, on
Jnanasutra. He too left this world by disappearing into a sphere of
light, leaving his disciple Vimalamitra his own testament ʻFour
Methods of Contemplationʼ, Shyak Tab Shyipa.
http://www.knamdrol.org/nyingthig-transmissions.pdf