Antichode, it's all a matter of the solvent being just polar enough to dissolve the impurities but not polar enough to dissolve the mescaline (the most polar alkaloid present). So a binary solvent mixture could be developed using many different solvents. For example, naphtha and IPA, or heptane and acetone, etc.

The great thing about a binary solvent mix is that you can control just how polar the solvent mix is by adjusting the ratio between the two solvents.

The cleanup step for mescaline is the opposite for the cleanup step of bufotenine. With cacti, mescaline is the most polar alkaloid, so you need a solvent mix that is just polar enough to dissolve the impurities but not polar enough to dissolve the mescaline. With bufotenine from cebil, you need a solvent just non-polar enough to dissolve the bufotenine, but not the more polar impurities.