This ts letter from Arthur Koestler was sent to Dr Thomas Kovari (Kövári Tamás) who had escaped from Hungary in 1956. The letter to 'Dear Mr. Koevari' - indirectly described by Koestler as a fan - was written from the Berghotel 'Böglerhof', Alpbach, in the Tyrol, Austria, on 2 July 1959. It is signed in Koestler's hand. Koestler thanks Mr. Koevari for the trouble he has taken to point out a passage... a 'howler'.
Although the title referred to is un-named, it is The Sleepwalkers, a history of man's changing vision of the universe, published in 1959 (London: Hutchinson).
The letter states: 'The formulation on page 506 was indeed very careless'. It goes on...: 'The "spiral" was meant metaphorically, referring to a meteor entering the earth's atmosphere [...]'. Koestler tells Mr. Koevari that he hadn't noticed 'an even more striking howler on page 394'.