Cacti vary greatly in alkaloid content, obviously. The bridgesii a friend has are extremely potent, more so than the pachanoi or peruvianus he has tried.
An individual on another forum is performing an experiment with fresh cacti, chopped and dried and ground. 39g of each of the three species was extracted using NaOH and H2SO4. While he hasnt(to my knowledge) finished, the first two evaporations of acidic water(0.1% H2SO4) indicate that the order of alkaloid content would bee(with his particular cacti) bridgesii,pachanoi, peruvianus
HOWEVER, as mr cactus said, bridgesii has MAOI's, a cactus-huasca. While mescaline accounts for half of the alkaloid content, the other alkaloids boost the effects.
Peruvianus has mescaline as its sole active alkaloid. So while the overall yeild may have been less, he is confident that the mescaline content is higher.
Does anyone have any experience using cold dry MEK to wash mescaline sulfate crystals?
But back to the OP's question: You could probably use 40g if it is the green dermis layer and the slightly lighter green, as this is where the highest alkaloid concentrations are. You could also extract it using various teks available online, so as to have a point of reference in the future for THAT suppliers product...remember that half of alkaloid content is mescaline but the other alkaloids enhance the experience. Use that information how you will, but Achuma is the most powerful cacti ally, IMHO