Here's a simple water based extraction for San Pedro cactus.   
   
   
Preparing a Steam Bath:   
   
Put a pot on the stove, and then put a large Pyrex bowl on top to help get the water level right.   
Place a desk fan near the pot and prop it up so that can blow directly into the bowl.   
Remove the bowl then fill the pot with water so that the water is not quite touching the bowl.   
You will need to use enough heat to simmer the water, so that when the bowl is on top, a little bit of steam will be escaping, but not too much. If the water is boiling madly and the bowl is making alarming noises as it lifts off the top of the pot, the heat is way too high.   
Make a note of the right setting on the ovens hob. Interestingly different hobs on the same oven can have different correct steam bath heat settings.   
   
If you are lucky enough to have a very large enamel lined oven hob safe pot you can use that instead for evaporating this down, but you will need to stir it almost constantly as the extract on the bottom can get stuck and burnt to the bottom. This isn’t as much of a problem with Pyrex bowls. Metals and acids react together (especially aluminium) so I would only cook extracts in glass or enamel. Stainless steel might be alright to use, and I heard that at high altitudes using a stainless steel pressure cooker is very good for cooking San Pedro. But I don’t know if stainless steel reacts with acids or not.   
   
   
The Extraction:   
   
Use roughly between 1.5 litres and 2.5 litres of water per dose and use the juice from 1 lemon, this will be divided into 3 cookings.   
Place the cactus in an enamel lined pot, then add ½ of the lemon juice.   
Cover fresh cactus with water. Dried cactus soaks up water so continue to add water and check so that after it has swelled it is covered with at least twice as much water as cactus.    
Simmer the cactus for 20 minutes.   
Then pour the liquid into a large Pyrex bowl through a plastic strainer.   
Put the bowl on the steam bath and turn it on.   
Add the cactus pulp back to the pot along with more water and lemon juice and cook again for 20 minutes, then filter and add the liquid to the steam bath.   
Do a 3rd cooking, then filter and squeeze the pulp against the strainer with a spoon to get as much as possible of the water out.   
Keep the steam bath going until the liquid has evaporated down to 200 ml. Swishing the bowl around speeds the evaporation. Stirring can help if there is too much liquid to swish the bowl around, but use a glass stirring rod or a wooden spoon handle.   
After it has cooled down and you’re prepared, drink it in 1 gulp.   
  
  
Hearsay:   
   
The taste can make people nauseous and many people find that if they try to slowly drink it the nausea prevents them from drinking enough.   
   
I heard that fresh cactus is more slimly so it would probably be better to use dried cactus. But don’t cook Peyote in this way as heat destroys much of it’s other compounds and it is best used fresh. I heard that when chunks of it are sitting in the stomach this can make you nauseous, so chew it until it’s a liquid, then swallow.   
   
I heard that women should avoid taking cactus during their period because it can make them bleed a lot. The lady said she was alright afterwards, but at the time she found it was pretty scary. 
    _____________________________________________________________