Their sidebar explaining IQ scores seems a little silly. I'd like to see a citations for average scores of Nobel prize winners. Also, who went back in time to administer an intelligence test to Mozart?
IQ is just defined in terms of standard deviations. Having an IQ of 130 means you are 3 standard deviations smarter than average, i.e. in the 99.7th percentile. Presumably, they just put Motzart in the top 99.xxxxxx% percentile by guess and calculated the resulting IQ.
Of course you have to remember that different tests use different standard deviations. For example, Mensa here in Finland uses a test with standard deviation of 15, so 130 is "only" two standard deviations smarter than average. The point is, the scores are meaningless without knowing the standard deviation used.
IQ tests are normed for a standard deviation of 15 points, not 10. (And I'll bet you knew that but got distracted by the '3' in 130. The "D'oh! Effect" -- a side effect of our associative memory architectures.)
Also, who went back in time to administer an intelligence test to Mozart?
A very astute question. IQ scores are specific to a particular test taken at a particular time, even when comparing IQ scores according to today's standard score definition of IQ for test-takers taking several tests very close together in time.
(See the sortable table, with reference to the original publication, at this page anchor location on Wikipedia. The same table appears at the page anchor link below. ALL of the Wikipedia articles on human intelligence and IQ testing need a lot of updates, because they have been subject to frequent edit-warring, but that table is quite useful.)
Nobody has an IQ score from more than about a century ago. The current standard score definition of IQ, performance on a cognitive test with the population median set at 100 and performance two standard deviations above the median being called IQ 130, began with the Wechsler adult tests in the 1950s and spread to child testing by the 1970s, and is now pretty nearly universal. But even with that definitional issue kept straight, an individual person's IQ score can bounce up and down over time, and by any kind of testing theory we can never be completely sure of a person's "true" score, as any score on any occasion of testing is an estimate of the test-taker's behavior on other occasions or with other item content. Honest IQ test-givers report scores with an error band around the score, as has always been done, for example, by the psychologist who has tested my children for appropriate educational placement.
The very excellent book Terman's Kids: The Groundbreaking Study of How the Gifted Grow Up by Joel N. Shurkin
gives the full back story to the silly estimates you see of historical figures who lived before the era of IQ testing, which were mostly made up by Terman's collaborator Catherine Cox. Her procedure was justifiably laughed at by Shurkin as he described it: she counted the lines in biographical reference works on different historical figures, and supposed that the people in history who got the most ink probably had the highest IQs. There were always plenty of anomalies in her results from the very beginning, and no one takes them seriously anymore.