David, thank you for culling together a considerable amount of valuable Buddhist material.

No other collection of sources in the world’s literature can come close to the Buddhist, for such a rich array of oral tradition. And, the congruence of Buddhism and Theosophy, especially with the issue of self versus Self should be all the more reason to pursue this direction, for it teaches us that the Dweller at the Threshold is our lower self, which must be snuffed out, as another Buddhist textbook, the Voice of the Silence, proclaims.

These Buddhist records would indicate previous accounts going back over periods of what can only be described as a historicity of previous Buddhas, i.e., a primitive Buddhism tradition, which would have attracted a reason for such record-keeping in the first place. Buddhist statements within that line indicate there were previous Buddhas and Bodhisattvas and that would indicate, from a theosophical standpoint, previous root-races of civilizations going back probably millions of years.

It is safe to say, much has probably been lost to us from the past. Probably equal to if not second best would be the Hermetic or Trismegistic material. Statements handed down to us from ancient historians state the Hermetic literature was vast indeed but looking at what has come down to us is paltry to what we should have. The interventions of early Christian writers and recorders did not help maintain that literature, due to their intervention of their own anthropomorphic rewrites which would tend to beg the question whether certain material was Hermetic at all and may have, due to that fact, been ignored or thrown out. The vast amount of Greek and Roman literature having been destroyed, much of it probably due to the Libraries at Alexandria, Egypt would lay bear the fact that certain parts of humanity do not care much about preserving past literary output.

Perhaps the Hindu purāṇas would be a third best, however due to the obvious rearrangement of that literature and its metaphorical and allegorical tellings, no doubt clearly mixed with historical indications, it will take a team of dedicated researchers an extensive period of time to sort it all out, reserved for the future. I believe all the purāṇas came down to us from one very large mahāpurāṇa. But, the time for sorting out the purāṇic conundrum is long past.

One thing is clear, based on the Buddhist oral traditions: We are dealing with the passing down through the ages by observers, indications of inspection from the past, millions of years ago and long before paleontological science has given us any hint of it. Dig deeper!