I wanted to comment on the article LSD and Samadhi by Viveka Singh.
A reader asks if the samadhi they experienced under LSD was real, and Singh describes it as a mere projection, i.e. a person has read about samadhi, takes LSD, and then the mind is merely manifesting a projection of their ideas about samadhi as a kind of LSD dream.
I suppose that could happen, however Singh sounds a bit like a Hindu fundamentalist who wants to steer people away from drugs simply based on dogma. Which is maybe not the worst idea, but I would make the case that these drugs can be used skillfully.
The psychedelic drugs can help quite a bit in terms of getting someone to a strong experience of samadhi (jhana). In this sense they are like spiritual steroids, with the possibility of giving one access to higher concentration states than they may usually have access to, or giving one a stronger experience of the qualities of these states.
We have initial research showing that there are similarities in the
brains of experienced meditators (Brewer) as compared with people on a
high dose of psilocybin (Carhart-Harris), so all of this shouldn't be
Most people who are familiar with these drugs have at least heard stories of people having some kind of big experience of bliss and light while on a psychedelic. This would typically be an experience of 2nd jhana, a strong absorption into the area of the A&P (the so called arising and passing) on the Progress of Insight originally mentioned in the Vishuddhimagga, a 5th century commentary. These states, if powerful enough, qualify as genuine mystical experiences on scales developed by Hood and Pahnke.
I think of the Vishuddhimagga (the Path of Purification) as mainly being a whole lot of ways to do jhana practice, but it does include a small bit about the Progress of Insight. Other people talking about the Progress of Insight include Mahasi Sayadaw, and we also have Daniel Ingram's take on it.