• Psilocybin Mushrooms, any of various species of mushrooms containing psilocybin and psilocin.
• DMT (dimethyltryptamine)is considered by some to be the most powerful, naturally occuring entheogenic substance...however, it is not normally orally active. The enzyme monoamine oxidase breaks down the DMT before it can enter your brain. However, nature is rich in plants containing monoamine oxidase inhibitors (MAOI's) which temporarily stop this enzyme from breaking down many chemicals in your body, including DMT. When South American Indians, and other peoples, combine plants with DMT and plants with MAOI's, they come up with a potion, called ayahuasca, yaje, and other names, and the use of the MAOI ingeniously allows the body to process the DMT. Of course, the shamans would say they learned this secret from the plants themselves, nontheless, this shows a very sophisticated scientific understanding of botanical compounds.
  Another traditional form of DMT is called yopo -- it is a powerful snuff, and does not rely on an MAOI, since the DMT gets directly into the user's bloodstream. I have not heard any tradition of smoking a DMT preparation, though today many people do smoke synthetic DMT.

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Lysergic Acid

• LSA (lysergic acid amide)is a natural chemical found in various plant sources: The seeds of Morning Glory and Hawaiian Baby Woodrose,
  and in the ergot fungus that would, from time to time, infect grain such as barley, consuming the populace in a mass trip often accompanied by ecstatic, communal dances.
  
• LSD (lysergic acid diethylamide) is a synthetic, man-made chemical, derived originally from the lysergic acid in ergot by Albert Hofmann

Amanita Muscaria

Amanita Muscaria is one of the most ancient, and sacred "drugs" ever to be used by man.
We owe much of our modern understanding and interest in this Holy Sacrament to

• Nicotiana Tobacum is the tobacco we are all familiar with. Cigarette smoking is one of the greatest diseases of the modern era. N. Tobacum contains large amounts of nicotine, a highly addictive drug. The colonists discovered this tobacco in the Carribean and imported it to North America, where they grew large cash crops, disrupting the ecosystem in order to turn a profit, profits which continue to multiply as much of the world's population is addicted to chemical-lade cigarettes, more addictive and more harmful than N. Tobacum in the first place. The Carribean natives likely used N. Tobacum in balance with their lives, and thus healthily. There was a tobacco native to North America in the first place,
  
• Nicotiana Rustica contains less nicotine and instead possesses entheogenic compounds.
  

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  Harmala

  
  

  Harmala, Harmine, Harmaline

  Harmala and related chemicals are naturally-occurring MAOI's. Although they can be used by themselves, these chemicals are often traditionally used to enable the oral absorption of DMT in the potion Ayahuasca
  many sources of these compounds exist...
  
  In South America,
  
  • Banisteriopsis Caapi
    
    
  • Syrian Rue
    

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    Ayahuasca

    .