Genius ceiling IQ
In 1916, Lewis Terman invented the IQ scale, defining the number "100" as average, and 140+ genius or near genius. This is classified as the "basement IQ genius level", meaning that one assigned or determined to have and IQ at 140 or above is "genius or near genius" according to Terman.
In 1926, Catherine Cox and Maud Merrill, under the supervision of Terman, ranked the top 300 geniuses from the Cattell 1000, and assigned each of them two IQs, one before age 16 (see: AI IQ Ratings), and the other (AII IQ Ratings) being their early adulthood IQ, up to the about their late 20s or so, based on their accomplishments, in each age group, with respect to others of the same age (see: Cox-Terman-Merrill IQ scale). The "genius ceiling IQ", from this study, was loosely defined by the following quote:
- “One rater (Merrill, 1925) has scored on the basis of the record of Goethe’s youth an IQ of 225. Goethe’s true IQ may in the history of mankind have been equaled in a few instances; one may well wonder whether it has ever been exceeded?”
- — Catherine Cox (1926), Early Mental Traits of 300 Geniuses (pg. 163) 
In other words, according to Cox, Merrill, and Terman the ceiling IQ in 1926 was "225", but we may wonder whether it has ever been "exceeded". We not that their study only looked at geniuses of adulthood age in the period years 1350 to 1850.
The top AI IQs are shown below, where we can begin to see a sort of "ceiling effect" as to when or where the top of the genius scale ends:
In this study, the highest IQ assigned was "225" assigned to Goethe by Maud Merrill. When the finalized book was published, the mean IQ calculations, done by Cox, Merrill, and Terman, assigned the genius ceiling IQ to be 210 assigned to Goethe.
In 1995, Tony Buzan and Raymond Keene, Book of Genius, wherein they attempted a ranking of the 100 geniuses of all time, defined the genius IQ ceiling as follows:
In Aug 2010, Libb Thims merged the 300 Cox-Merrill-Terman geniuses with the 100 Buzan-Raymond geniuses, to arrive at the following mean IQs for ceiling geniuses:
In Sep 2010, Thims, having found the infamous "IQ of 400" of Adragon Mello (James de Mello) (1976-), and others, had arrived at the following historical of "genius ceiling IQ" attempts:
Here, we see the 1940 Abraham Sperling reported psychology-tested IQ of William Sidis, a few years before he expired; along with the IQs of the Michael Kearney (1984-), Ainan Cawley (1999-), Adragon Mello (1976-), as determined by their parent's calculations, when they were in the single digit ages. We will note that the discovery of the Mello estimate (see: Thims 32), was what prompted Thims into re-calculated the IQs of all geniuses and cleaning out fake IQs.
On 16 Apr 2020, Libb Thims, taking the century-long CPBT IQ means into consideration, namely the following two IQs: Newton (IQ:199) and Darwin (IQ:175), lowered the "genius ceiling IQ", of his top 2000 geniuses and minds rankings, from 225 to 210, as follows:
- Goethe (225|#1) → (210|#1)
- Newton (220|#2) → (205|#2)
- Einstein (215|#3) → (205|#3)
- Maxwell (210|#4) → (205|#4)
- Gibbs (210|#5) → (205|#5)
- Clausius (205|#5) → (195|#7)
- Vinci (200|#7) → (200|#6)
- Young (200|#8) → (195|#11)
- Helmholtz (195|#9) → (#195|#10)
- Aristotle (195|#10) → (195|#8)
- Galileo (195|#11) → (195|#9)
In other works, in the 2010s, Thims, while growing this top 2000 geniuses and minds list, had Einstein, Newton, and Gibbs ranked "above" in the 215 to 225 range, which does not corroborate with the fact the CPBT IQ of Newton is 199 and Darwin that of 175. Hence, Thims "compressed" the ceiling, so to say, to align more with realism. The rest of the IQ rankings, in the 140, were compressed accordingly.
The following are quotes:
- “So I say, in your child-find, since the Government has now changed the definition of retardation to a ceiling IQ of 70, and if the child has an IQ of 70 or above, he is not retarded, we are going to find more children with IQ's under 70 who are coming into special education. I don’t know what they are going to be designated, learning disabled, or whatever.”
- — Theresa Travalino (1981), “Statement During Field Hearings on the Education for All Handicapped Children Act” 
- “The smartest person on earth, whoever he or she is, probably has the IQ between 190 and 200. There are reasons to say that Feynman has belonged to the hundred of smartest people on earth, i.e. the IQ above 180 or so.”
- — Lubos Motl (2018), “Comment on Feynman’s IQ of 125” 
- Terman, Lewis. (1916). The Measurement of Intelligence: an Explanation of and a Complete Guide for the Use of the Stanford Guide for the Use of the Stanford Revision and Extension of the Binet-Simon Intelligence Scale (classification of intelligence, pg. 79; I.Q., pg. 53, etc.). Houghton Mifflin Co.
- (a) Cox, Catharine. (1926). Genetic Studies of Genius. Volume II. The Early Mental Traits of Three Hundred Geniuses (Arc) (pdf) (ratings, pg. viii; Goethe IQ 225, pg. 163). Stanford University Press.
(b) Cox IQ (subdomain) – Hmolpedia 2020.
- Ainan Cawley (talk page) – Wikipedia.
- Anon. (2020). “Former Smartest Teens: Where Are They Now?”, THe Best Schools, Oct 29.
- Abraham Sperling – Hmolpedia 2020.
- Anon. (1981). Field Hearings on the Education for All Handicapped Children Act (pg. 35), US Government.
- Was Richard Feynman’s IQ really 125? (2018) – Quora.
- IQ testing (ceiling effects) – Wikipedia.