I did some brief googling on the topic earlier, and the best I could find was "anywhere from 5-20 milligrams of psilocybin per gram of dried mushroom". Which is very unhelpful for working out whether these people took a strong dose by recreational standards. :D

It's more or less impossible to know the psilocybin content of any one specific mushroom offhand, and it can vary greatly even between mushrooms from the same batch, thus microdosing with actual shrooms is an inexact science. You can grind them up into powder and mix it together to average it out, but the total psilocybin will still be an estimate at best.

There is 4 aco dmt, which is supposedly gets converted to psilocin just like psilocybin and I don't believe is illegal in the US, however it degrades very easily into psilocin if stored incorrectly so can be dicey to have since psilocin itself is still illegal.

Erowid dosage pages can be helpful: https://erowid.org/plants/mushrooms/mushrooms_dose.shtml vs. https://erowid.org/chemicals/psilocybin/psilocybin_dose.shtm...

Isn't uptake through digestive tract unreliable? Mental disorders require extremely precise dosing, therefore probably should administer intravenously.

Most psychiatric medications are applied through eating pills, mind you, so this seems like a criticism that applies to a vast field of medications...