Yeah, like globalloon said its best to get finite instructions off erowid. But I’ll give you some info as well.
I warn you though, it’s a tedious job!
There’s 3 layers to the cactus, the pale green skin, the dark green juicy part just under the skin, and the core of the cactus, which would be white/yellowish. Anything, apart from the dark green part, must be thrown away. The dark green, juicy part is where the highest concentrate of mescalin is (along with a few other substances as well Im pretty sure).
You want to peel the skin of the cactus off to reveal the dark green underneath. Be careful not to peel to deep and waste the dark green part. You must peel the whole branch; and the skin has a tendancy to rip off in very tiny pieces.
After you’ve peeled the entire branch of the cactus, you cut it in half (longways) and then cut those halves in half and start using a knife to strip away the dark green parts. When you’re left with a plate full of dark green strips, some white stalks on the table and a bunch of skin peelings. Throw everything but the dark green strips away.
Then it’s as simple as drying the dark green strips in the sun or oven and then bam! you eat them. Of course you could go one step further and crush them up into a powder and stick them in gel caps, which are like 4 bucks for a pack from your local chemist. One thing with the powder is that if you keep it in your mouth to long, it becomes the consistancy of snot; not very nice heh.
As for dosages I’m not -exactly- sure, but I had about a foot’s worth of stalk (after it had been processed of course) and after about 2 hours I was tripping mad ways and it felt like I had dropped as well.
Also, I’ve tried smoking it with a few friends (powder form) and if you have about 3-4 bowls and wait about an hour and a half, it gets you pretty brained out and feels like a weak pill. Mix it with green and go for yoru life.
One thing I must make very clear. It is probably the worst thing I have ever tasted! When smoking it, it tastes half as bad as it does when eating it. Kind’ve like smoking cloves. Hahah, so be sure to have a drink on hand, preferably coke or orange juice or something else with a distinct strong flavour.
Well I hope that helped out. And have fun with your mescalin 🙂
