I have mixed all three classes of psychedelics, and one of the most amazing, beautiful, mind-bending, and spiritual experiences is what follows. Before I hear about set and setting, I have done this several times, and the effects are pretty consistent. I think there is just something about the combination of the compounds I chose that makes it special.
It should be started first thing in the morning on a day where your attention is not required by anyone and in a place that you are positive you will not be disturbed in. I found it best to have this experience in a rented cabin or something similar during the summer. I found that 1-3 extremely close friends is ideal for this experience. The night before you should prepare plenty of snacks and light meals such as sandwiches, fruits, gespatcho, and things like that, as well as plenty of juices, sodas, citrus water, and a huge supply of ice. Also, have music of your choice queued up for at least 12-14 hours. Anyway, here is the method I follow:
T-1:00: 60mg Ondansetron or equivalent dose of other 5-HT3 antagonist, to counteract the nausea without messing up the rest of the experience like other antiemetics potentially can.
T+0:00: 40mg αMT orally, followed by a LIGHT snack (as in a piece of toast or something similar)
T+0:45: 35mg Methallylescaline orally, followed by another light snack.
T+1:00: 200μg LSD sublingually and 10mg 4-HO-MiPT orally. The first time I had this experience I dosed 5mg of 5-MeO-MiPT at this point, but once the reuptake inhibiting effect of 5-MeO-tryptamines became known, I replaced it with 4-HO-MiPT, which also made the experience far superior than it was with the 5-MeO-MiPT.
So that's it for the dosing. Basically, the effects are incredibly special and totally unique. The effects seem to come in waves, in a much stronger way than anything I've ever experienced before or since, with alternating feelings of total sobriety and complete psychedelia. There is amazingly strong synesthesia, with the music seeming to send pulses of fractals and color exploding in your visual field which then translated to amazing tactile sensations and, even on a few occations, tastes and smells. With eyes closed, expansive alien scenes spread out before me. It was easy to get lost in this closed-eye world, to the point that I forgot my eyes were closed and even began to experience entity contacts. Emotionally there was an immense feeling of closeness and comradery and we all came out of the experience feeling as if our friendship had been deepened and given a special meaning. Honestly this combination has shown itself repeatedly to be one of my favourites, but it is very intense and shouldn't be taken lightly by any means.
I figured I would share this because the concept of mixing substances from all 3 main classes of psychedelics, and seeing if they play nicely was mentioned, so I figured I would share my experience with doing just that to give people some idea of what they can expect. Hope this information is useful or entertaining to someone!
P.S. I forgot to mention that its also a very good idea to have something to come down with when everything is all said and done. Opiates work well, as do benzos to a lesser degree. On one experience we used chlomethiazole to come down with, but given the fact that it's pharmacology is not entirely known, it might be a good idea to pass on that one. Anyway, that about covers everything.