The Yangti Nakpo (Tib. ཡང་ཏི་ནག་པོ་, Wyl. yang ti nag po), the Black Quintessence, or, to give its full title, The Single Golden Letter of the Black Quintessence (ཡང་ཏི་ནག་པོ་གསེར་གྱི་འབྲུ་གཅིག, yang ti nag po gser gyi 'bru gcig), is a cycle of Dzogchen teachings that includes practices focusing on dark retreat. It was brought to Tibet by Guru Rinpoche and hidden as a terma by Yeshé Tsogyal. It was discovered by Dungtso Repa 'the later' in the fifteenth century and rediscovered in the nineteenth century by Trulshik Dongak Lingpa. Therefore there are two lineages for the Yangti Nakpo: the long lineage transmission (ring gyu) from Dungtso Repa and the short lineage (nyegyü) through Trulshik Dongak Lingpa.
- Kunsang, Erik Pema. Wellsprings of the Great Perfection. Rangjung Yeshe Publications, 2006, pp. 294-298
- Shabkar Tsogdruk Rangdrol, The Life of Shabkar: The Autobiography of a Tibetan Yogin, translated by Matthieu Ricard (Ithaca: Snow Lion Publications, 2001), page 63.