The historically use of psilocybe mushrooms dates back thousands of years. Dozens of caves around the world have colorful mushroom shapes, and even people shaped as mushrooms. Figurines in the shape of mushrooms have been found all throughout Mesoamerican culture. Some people even believe that the use of these mushrooms extends far beyond ancient man.
Terrence McKenna has proposed an idea whereby prehistoric hominids (as in Australopithecus africanis and Homo habilis) living in Africa had a diet that consisted of psilocybin mushrooms, most likely of the Panaeolus or Psilocybe genera. He even formulated a theory surrounding the mushroom's use that involves evolutionary progress and the development of simple language, around the mesolithic period. He hypothesized that ancient man, using the help of the synesthesia that may result from ingesting psilocybin mushrooms, slowly evolved the ability to formulate pictures in another human's mind through the use of vocal sounds.
His theory has more evidence than one might expect. As stated above, caves throughout the world have painted mushrooms. Statuettes of mushrooms and shamans holding them is unmistakable evidence for their use as entheogens and even medicines by many cultures of the ancient world. The Aztecs and the Mazatecs were very well known for the use of magic mushrooms as not only a right of passage, but for divination and healing as well. During the time of the Spanish Inquisition, the use of magic mushrooms basically ceased due to the fact that the Spanish believed the mushrooms enabled the Aztecs to communicate with the devil. The use of magic mushrooms was cast down upon and demonized by Christianity, Islam, and other religions for centuries thereafter.
In 1955, R. Gordon and Valentina Wasson were the first Western people to participate in indeginous magic mushroom ceremony with a tribe of the Mazatec people. There were simply astonished, and they publicized their experiences in Life Magazine in 1957. Meanwhile, with specimens that the Wassons had grown, Albert Hoffman, the man who synthesized LSD, identified the psychoactive chemicals within the mushrooms.
Inspired by the Life Magazine article about the Wassons' experiences, Dr. Timothy Leary, a psychology professor at Harvard University, traveled to Mexico to experience the mushrooms firsthand. Upon returning, he and Richard Alpert concieved the Harvard Psilocybin Project which aimed to study the spiritual and psychological effects of psilocybin mushrooms and other hallucinogenic drugs. He was eventually fired from Harvard, leading to his lifelong devotion to spreading and supremely glorifying the psychedelic experience with his famous phrase "turn on, tune in, and drop out."
The effects of psilocin are very similar to LSD both somatically, psychologically, and subjectively. They do have subtle differences, however. When psilocybin is ingested (which is by far the most abundant chemical in magic mushrooms besides psilocin), it is quickly metabolized into psilocin, which is responsible for nearly all of the effects of the drug.
The onset, depending on method of preparation, usually occurs within twenty to forty minutes, with the user reaching the peak at around the hour to ninety minute mark. The effects slowly decline over the following four to five hours, usually resulting in a certain degree of afterglow (essentially the opposite of a hangover) that may last until quality sleep or even days after the experience.
Dose is generally between a quarter of a gram to as much as five grams of dried material (2.5 to 50 grams fresh) depending on the species potency. 0.25 grams is considered by almost all users to be not nearly enough to produce any effects, but some individuals get a moderate psychedelic effect at this level. Most people ingest an eighth of an ounce at a time, which is 3.5 grams. For a first-time user, this is probably excessive. People have been reported to take as much as ten and twenty dried grams, with people that go even further than that (a man documented his experience in retrospect about a forty gram dried magic mushrooms experience, which is a colossal amount that requires months and months of preparation to make sure your mental stability is concrete enough).
Physical effects of ingesting psilocybin mushrooms are primarily mild to severe mydriasis (pupil dilation) along with slight muscle tension and increased sweating. An increase in heart rate can occur, but this is basically akin to slight physical activity (brisk walking).
As with other hallucinogenics, the overall emotional outcome is guided by set and setting. A bad trip can result in feelings of fear and alienation, but the emotional impact of a positive experience is often described as transcendental, enlightening, euphoric, and overall vastly enjoyable with intense feelings of wonder. In high dose experiences, many people report feeling contradictory emotions at the same time or even emotions that they've never experienced before.
The sensory aspect of the psilocybin experience, as with most other hallucinogens, is the desired and most pronounced effect. Around the thirty minute mark, motion in the periphery of vision becomes apparent. "mother of pearl" surfaces, as in surfaces that have repeating textures such as wood, grass, sand, gravel, etc., start flowing and rippling. Colors vastly brighten and visual acuity increases, resulting in halos and auras that surround pinpoints of light. Tracers may appear behind motion, especially when the mobile object is of contrast to its background (such as football streaking across a blue sky). Objects grow, shimmer, shrink, stretch, compress, and fuse together. Perspective distortions cause macropsia and/or micropsia (reality appearing larger or smaller than normal), which may sometimes occur simultaneously. Colorful patterns present themselves on walls and surfaces and behind closed eyes. When the eyes are closed, scenery may unfold and play out with fractals and simple geometric shapes. Synesthesia often occurs with moderate to high doses, wherein the user may experience "seeing" sound and "hearing" color, among other sensory anomalies.
Magic mushrooms have long been used as medicines from Asia to South America. Recent studies have essentially proven the beneficial effects of psilocybin mushrooms on patients with cluster headaches and alcoholism. Some even suggest that the treatment of OCD, OCD-related depression, and body dysmorphia disorders can be cured with psilocybin mushrooms nearly immediately and for periods of up to months.
The dangers are few, but they can be deadly dangers. The most obvious danger is picking or ingesting the wrong variety of mushroom. Typically, it won't be fatally poisonous, but on rare occasions people have accidently eaten some of the most toxic and dangerous species in the world. It is noted that while the mushrooms' psychoactive ingredients are nontoxic and very physically safe to ingest, the mushrooms may also contain other inactive chemicals to support its vitality and other systems which may be slightly toxic. This is most commonly seen through the nausea that people experience before their "trip" begins. Most likely these chemicals will be no where near fatal amounts in as little as a few hundred dried grams, but take precaution.
As with LSD, uterine contractions occur, so anyone who is currently pregnant should never ingest magic mushrooms. Also, some people believe that underlying psychosis-like symptoms may result, much like the use of LSD. The key word is underlying, meaning predisposed, mental illnesses may be very slightly exacerbated by ingesting either psilocybin mushrooms or LSD. The chemicals in magic mushrooms virtually have no pure potential to cause psychosis.
"Flashbacks" can occur as well, of which the danger, prevalence, and intensity are vastly over-exaggerated by the media and other political systems. Flashbacks are a result of the brains sudden recurring ability to "open" its natural filters, thus allowing a significantly increased amount of information from the body to be processed. It's not technically harm, it's actually improvement in the brain's functioning, but most people see flashbacks as debilitating.
While they do distort perception, flashbacks will never exceed the intensity of any psychedelic experience, nor will they come close to it. People who have not experienced them often claim that what you see are true hallucinations such as elephants and colored monsters running across roadways or threatening you in some way. In reality, this is nothing what flashbacks are like. At most, colors can brighten, small objects can stretch, imagination can increase, distance can slightly distort, etc.
Physical -- 0
Psychological -- 0 - 3 (for the same reasons as LSD)