Atisha, the eleventh-century Indian Buddhist scholar and saint, came to
Tibet at the invitation of the king of Western Tibet and initiated the
period of the "second transmission" of Buddhism there. In this, his most
celebrated text, he set forth the entire Buddhist path within the
framework of three levels of motivation, represented by the Hinayana,
Mahayana, and Vajrayana paths. His teaching became the source of the
lamrim tradition.