Mexicana is one of the most famous Psilocybine strains that have been in use by Mazatec Shamans since Aztec times. Luckily, this strain produces Sclerotia, also known as Truffles. 
This Truffle strain brings a rather soft high and is therefore ideal for beginners. Nonetheless, its potency should not be underestimated. 
Mild effects are already present at a dose of 5 grams, while 10 - 15 grams can result in a medium to strong effect. First effects are likely to be felt after around 15-30 minutes and last…..

You can eat Truffles or use them as a tea (let it simmer for 20 minutes, don't let the water boil).

BE AWARE that these amounts are averages and can vary from person to person. Always start with a low dose.