The first IQ society in history to precondition admission on the basis of examinations, excluding the Chinese mandarinate, is Mensa International. It was founded because two men happened to meet on a train. Though the reasons Ware and Berrill decided to found a high IQ club are the subject of dispute, it is likely that they realized from their first conversation that although they came from different backgrounds, they were able to communicate and had much in common. They hypothesized that what they had in common was intelligence, and decided to see if a society of people selected for intelligence (using the only means available, IQ tests) would also have much in common. 
They decided to focus on people whose intelligence would place them at or above the 98th percentile.
Beyond the 98th percentile
In the late 1930s, Dr. Leta Hollingworth's groundbreaking research, which led to the publication of Children Above 180 IQ (1942), suggested that there is a group of people with extremely high intelligence who also have much in common and who are as different from people at the 98th percentile in IQ as people at that level are from the norm. That level, 180 ratio IQ, roughly corresponds with the one in thirty thousand level. Starting in the early 1960s, when the now-defunct MM was started, there were attempts to form societies accepting people at a level approaching this. The International Society for Philosophical Enquiry and the Triple Nine Society, both in existence today, were founded in the 1970s. They accepted people at the one in a thousand level, far short of Hollingworth's norms. There was a problem in going higher. Apart from certain scores achieved in early childhood, no available tests were normed at that high a level, and the paucity—by definition—of data at that level made such norming very difficult indeed.
There were two possible ways to overcome this obstacle. Either the raw data from standardized tests could be obtained and determination could be made if they could be normalized to Hollingworth’s levels, or new tests could be designed and normalized. In the late 1970s, it was the latter approach that was followed. Kevin Langdon and Ronald Hoeflin both developed high-range, untimed tests. Langdon claimed that his Langdon Adult Intelligence Test had a ceiling at the one-in-a-million level (176 IQ [or 171 using the academic-standard 15-point-per-standard-deviation system], or 4.75 standard deviations above the mean). Hoeflin claimed a considerably higher ceiling but the Langdon and Hoeflin tests are closely comparable, with Hoeflin's tests having ceilings only one or two points higher than Langdon's. These tests were given to a pool of about thirty thousand test-takers, recruited through Omni magazine, and the resulting data were used to develop norms. Langdon equated means and standard deviations; Hoeflin used equipercentile equating. Using these tests and norms, Ronald Hoeflin founded the Prometheus Society in 1982.  It was the second society to select members at the one in thirty thousand level, the first being Kevin Langdon’s Four Sigma Society, founded in 1976.
The pool of members was always limited by the number of people who had taken the Langdon and Hoeflin tests, and it was further limited when, in the 1990s, answers for some test questions were put on the Internet. However, there existed a large pool of potential members as tens of millions of people had taken standardized exams such as the SAT, which were, in effect, IQ tests. The problem was to normalize them. In 1999, Prometheus formed a committee of ten members, many of them experts in psychometrics, to attempt this difficult task. The committee produced a long report examining all reputable intelligence tests, determining which tests could screen at the four-sigma level (four standard deviations above the mean of a normal distribution), and what the appropriate scores should be. This report recommended that members be chosen based on scores in several widely known and researched standardized tests, including the SAT, the GRE, the Wechsler Adult Intelligence Scale, Cattell Culture Fair III, and others. This greatly expanded the number of possible members. Today, the number of members hovers around a hundred.
The membership roster is diverse. There are CEOs of high-tech firms, math professors, computer programmers, physics PhDs, army officers, dry cleaners, and NASA employees. Quite a few are involved with computer modeling of complex phenomena. As this list suggests, many members have much in common, and the officers try to link together members whose business or other interests complement each other. The society produces a 72-page magazine, Gift of Fire, published ten times a year, which contains many scholarly or speculative articles, along with poetry, artworks, and short stories. Perhaps the best-known article to appear in Gift of Fire is Grady Towers' essay, "The Outsiders". 
- Dan Barker
- Karyn S. Huntting
- Ronald K. Hoeflin
- Marilyn Vos Savant
- British Mensa, Limited (August 16, 2000). Obituary - Dr Lancelot L Ware, OBE, Fons et Origio of Mensa. Press release. Retrieved on 2006-07-26.
- Washington Post (November 16, 1997). Get Smart with High-IQ Society. Press release. Retrieved on 2006-07-27.
- Miyaguchi, Darryl (1997). Generic I.Q. Chart. URL accessed on 2006-07-23.
- Miyaguchi, Darryl (2006). Uncommonly Difficult IQ Tests. URL accessed on 2006-07-25.
- includeonly>Aviv, Rachel. ""The Intelligencer"", Village Voice, 2006-08-02. Retrieved on 2006-08-02.
- Miyaguchi, Darryl A Short (and Bloody) History of the High I.Q. Societies. URL accessed on 2006-07-30.
- Membership Committee (1999). "1998/99 Membership Committee Report". Prometheus Society. Retrieved on 2006-07-26.
- Material on some members of Prometheus and related societies can be found at http://web.archive.org/web/20010516033659/www.brokersys.com/~bahai/
- The Prometheus Society
- Towers, Grady M. (1987). The Outsiders, Gift of Fire, issue 22.