The King of Samadhi or the Samadhi Raja Sutra is one of the few sutras that discusses Mahamudra. Thrangu Rinpoche in this book gives a full length teaching on this sutra discussing Mahamudra, This sutra also gives the story of how the Buddha predicted the coming of Gampopa.

The original sutra of the King of Samadhi is several hundred pages long and we offer it a free PDF.

The book is presently out of print, so Namo Buddha Publicatons offers it as a PDF.