Many historical mystical experiences are triggered by asceticism. Restricting food, water, social contact, sex, oxygen — engagement in extreme darkness, extreme cold, fatigue, meditation. In short, one could argue, there is no such thing as "sober mystical experiences." They are an altered state of consciousness.
Importantly, the mysticism scale is not a “drug induced mysticism scale.”
The Pythagorean-Platonic tradition is rich — and let me be careful to say that I'm not making the claim that all philosophy is the same everywhere. But mystical concepts of unity and harmony are precisely perennial because of the shared nature of mystical experiences. Mystical christianity, mystical judaism, mystical islam, mystical buddhism, mystical taoism, mystical shintoism... The experiences have a lot in common. There are a number of surprising alignments between the Dao De Jing and Presocratic philosophy. I’d be happy to share.