One of Longchen Rabjam's "Seven Treasuries", this is a treatise on the four great samayas of dzogchen: ineffability, openness, spontaneous presence and oneness. This book contains the original Tibetan of the root text and autocommentary, with extensive quotations from Dzogchen tantras and masters such as Garab Dorje, Nagarjuna, and Padmasambhava.