This includes a translated excerpt from his 'Record of Teachings Received', in which he is discussing the Mani 'bka-'bum. It also contains translated excerpts from the Mani 'bka-'bum itself, which is a very important Tibetan treasure text attributed to Song-tsen Gam-po. If you're not familiar with it, I strongly suggest that you re this essay. It's very important in Tibetan culture and Buddhism.