The Book of Dzyan is linked to the books of Kiu-te or the Tibetan Buddhist tantras.
Specific authors and texts have been identified for the similarity of their teachings with the Secret Doctrine fundamental propositions. The Maitreya/Asanga’s works and the Jonangpa’s tradition are among them. The glimpse of the Wisdom Tradition was brought or transmitted by the Adepts in contact with the TS founders. Based on the HPB’s testimony and various letters from the Mahatmas, they were followers of Tibetan Buddhism practices, living or staying in Tibetan monastery for their practices like silent retreats. They may have been linked with one Tibetan Buddhist lineage more specifically (or maybe not). Identifying this may bring some more tracks to locate the original Book of Dzyan (or maybe not…).
In a book, first published in 1941, « The K.H. Letters to C.W. Leadbeater », C. Jinarajadasa commented at the end of the first letter :
« With this invocation to the Highest in C.W. Leadbeater to remember, and to be guided by that memory – to decide for the best - » , the letter ends with the initial « K.H. » of the name Koot Hoomi, which is not the Master’s personal name, but the title of his office as a high dignitary of the Koothoompa1 sect of Tibetan Buddhism.
(1) But pronounced Kethoomba, the Master informs Mohini Chatterje in Letter 59, The Letters from the Master of Wisdom, Second Series
This Letter 59 says : « However, the written name is Kuthoompa (disciples of Kut-hoomi), and its spelling is Kethoomba. »
Looking at the various sects and lineages in the history of Tibetan Buddhism, the closest to the Kuthoompa or Kethoomba seems to be the Kadampa (Kadam Tradition).
This specific lineage is in fact at the root, the foundation of most of the current existing lineages, and more specifically to the Gelugpa who are the « continuation » of the Kadampa.
Looking more in detail inside the history of this movement, this tradition was brought and installed in Tibet by the Bengali master Atisha Dipamkara (982-1054) and his principal disciple Dromtön Gyalwai Jungné (1005-1064). The flourishing of Avalokiteshvara and Tara in Tibet seems to be linked to this phase of their history. More specifically, quoting Thupten Jinpa – The Book of Kadam
“Although Avalokiteshvara was propipiated in Tibet before the tenth century, and although the designation of the seventh-century Tibetan emperor, Songtsen Gampo, as an embodiement of Avalokiteshvara most probably predates Atisha’s arrival in Tibet, the available textual evidence points strongly toward the eleventh and the twelfth centuries as the period during which the full myth of Avalokiteshvara’s special destiny with Tibet was established.”
The Kadam school (bka’ gdams) was identified soon after Master Atisha’ death , especially after the creation of the Radreng Monastery in 1056, not far from Lhasa. Atisha organized the entire corpus of the Buddhists teachings in his Lamp for the Path to Enlightment. He was the first to propose the teachings under the form a gradual approach to the Buddhist path (lamrin), based on two divisions : the lamrim proper, and the tenrim (stages of the doctrine). Tsongkhapa’s texts will follow the same format. Atisha wrote extensively on Buddhist Vajrayana practice, including Guhyasamaja, Cakra samvara, Avalokiteshvara and Tara.
Known as Atisha and Dromtönpa’s “secret teachings” (gsang chos), is the Book of Kadam, which some excerpts were translated and published (© 2008 Institute of Tibetan Classics).
Kadampa’s lineage went on up to the end of the sixteen century where it looks like if it disappears. In fact it cease to be a distinct school , partly due to the “new Kadam School” created by Tsongkhapa, but mainly because all other Tibetan Buddhism Sects had integrated the Kadam teachings in their core teachings. There was no more need for a distinct school. Even the Nyingma School often refers to the “Kadam Masters”.
So, the Kadam school being no more an active lineage in the 19th century, it does not help us much to know that Master K.H was a high dignitary of the “Koothoompa” sect, if it ever was the Kadampa sect who was referred to. Maybe it is only Jinarajadasa’s own comment.
However, looking at The Book of Kadam and other Atisha‘s works may be worth the “détour”.