Atisha, a Bengali meditation master of the 11th century, is the originator of this practice. The story is that at around age 50, he was invited to come to Tibet by a King of Western Tibet. Atisha refused saying he was too old to make the journey. The devout king was subsequently captured for ransom. His captors asked for the weight of his head in gold. The king’s subjects gathered the ransom, but the king told them to bring that gold to Atisha as an offering for his coming to Tibet. They did so, the king was killed and so Atisha really had no choice. He was instructed by his guides that while it would shorten his life, it would increase the life of the Dharma.
The suggestion is that when Atisha arrived in Tibet, the emphasis of the mediation practices had degraded into a display siddis. Siddhis, or accomplishments, are the powers said to come with many hours of practice. Powers like flying, manifestation of objects from thin air, resistance to fire and such. Jetsumna referenced Milarepa’s reputation with black magic as an illustration of the times. Atisha brought the practices back to the fundamentals. Jetsumna supposes that Atisha’s contribution is perhaps why the Tibetan teachings stayed on track, producing so many enlightened masters, and did not get lost into magical mysticism.
According to Jetsumna you do not just go study a text on your own. It has to be read to you by someone who has it read to them, who has had it read to them and so on.
I am hardly a qualified teacher of these texts, so please know this rendering and sharing does not count.