Tib., bi ma sNying-Thig: The Heart Essence of Vimalamitra
Name for the transmission lineage of Dzogchen teachings that goes back to Vimalamitra, a lineage that has been passed on orally (bKa'-ma) throughout the ages.
The 51 sections of these Nyingtig teachings belong to the Mannagde class of the Inner Tantras.
Sometimes, this collection is referred to as "the spiritual instructions that originated with Vimalaitra" (Tib., bi ma'i bka' srol snying thig).
Part of the text is dedicated to explaining the transmission of these Great Perfection teachings from Buddha Samantabhadra, through the various Indian masters (Skt., vidyadhara), to the Tibetan lineage holders. This part of the text is known as the "Great History of Nyingtig" (rdzogs pa chen po snying thig gi lo rgyus chen mo).