Comment by kstrauser
Truuuue, but that was John High-I-Quincy Adams, that one study estimated had an IQ around 170: https://www.acsu.buffalo.edu/~jcampbel/documents/SimontonPre...
Even if he didn't, there's a lot of evidence that Johnny Boy was exceptionally bright, to say the least. You can't really expect that level of writing skill from a typical 10 year old.
I'm not sure about the idea of retrospectively assigning IQ scores to dead people who never took an IQ test.
For what it's worth, I believe a reasonably intelligent child could have written that. Here's another letter, this one written by a 12-year old girl in 1842, which is similar to the other except for being, if anything, a bit more composed.
https://100yearsofstories.wordpress.com/2016/01/06/my-deares...
> My dear Papa,
> It is with much pleasure I write to you these few lines to inform you that our vacation will commence on the 18th of the month when I hope you will find me improved in all my studies in which I have done my best. Miss Sykes and Miss Martha present their compliments and hope though late you will accept their thanks for the very nice hare you were so kind as to send.
> With love to all at home, you remain my dear papa.