The pineal gland (third eye?) remains a mystery but seems to open to a direct experience of what is a very basic outline of the universe. Buddhist cosmology depicts this universe in 31 elementary planes. If one were to simply look at the animal world and its incredible diversity, one would understand that a single plane is anything but uniform yet it is still categorized or named one thing. How much more complex and diverse the other worlds must be -- from dazzling light-worlds (where devas wield creative power, which seems to be what Daniel Pinchbeck is referring to 6 minutes and 21 seconds in) to misery unutterable in the Downfall.
What is left out of nearly everything discussion of Buddhist cosmology, cosmography, and Abhidharma is the personally verifiable fact that these things are visible to successful meditators. This means that "speculations" on consciousness, its origins and detailed submoments, are not speculations at all. One can see for oneself. The Dharma invites investigation. The links of Dependent Origination are visible phenomena. Moreover, the various kinds of unseen beings described are visible with the scholar-practitioner Pa Auk Sayadaw refers to as the "light of wisdom" through the divine eye (Buddhist dibba-cakkhu).
Mental unification (collecting and calming the mind through right concentration, the Noble Eightfold Path factor samma-samadhi) makes it possible. Some measure of understanding and direct seeing are necessary for attaining the stages of enlightenment. Insight to be liberating is not an intellectual pursuit. It is a direct, one hesitates to say "shamanic" although that is approaching the degree of mysticism involved, experience. The experience is as direct as seeing and touching.* Although mind-expanding substances and other shamanistic pursuits across cultures may lead to glimpses of this amazing and spectacularly diverse universe, they in no way lead to liberation from it. Appropriate meditative practices (jhana and vipassana) lead both to seeing these things at will and practicing towards liberation if one chooses.
*If no one at WQ had attained to this level of direct experience and could verify the reality of these things, we would not talk about it.