A fresh shroom may contain up to 20% more active ingredient as the next. So I like to use dried ones, so I know what dose I do. Sugar, niacin and vitamin C decrease the effects.
A suggestion for the extreme and the hardheads amoung us:
BE SURE TO HAVE A SITTER WITH YOU!
Boil a small dose of bouillon for one person. When it boils, you add one dose of shrooms (2,5 grams of mexican from some internet source)to the soup. Boil this for no more than 2 minutes otherwise the active compounds will be destroyed. Pour the soup in a cup. Which is placed in cold water. Drink the hot soup as soon as you are able to drink it.
As you will probably not be able to finish the soup, the sitter needs to take the cup from your hand, so you can lay down. Good flight.
Alfa