There is even a sutta that strongly hints at the powers being solitary. In Anguttara-Nikāya 3.60, the Buddha is having a conversation with the brahmin Saṅgārava. After some discussion of these various kinds of powers, Saṅgārava says, “Only the one who performs this wonder experiences it and it occurs only to him.” This is totally congruent with these supernormal powers being a lucid dream. One can learn to enter such dreams via the mind-made body, which is known today as WILD.
