Koestler got his glimpse by working out Euclid's geometrical proof of the infinitude of the number of primes. That he was able to learn of the reality of the Infinite by a purely mathematical and precise method, without becoming a vague emotional mystic, so satisfied his highly intellectual and scientific nature that, in his own words, an "aesthetic enchantment" fell upon him. This developed until he became one with Peace never before known. The experience passed away, as it usually does, but it remained to haunt his memory. It inspired his journey to India and Japan several years later, where he spent a year trying to meet holy men and yoga experts. These meetings did not bring him what he sought, but his faith in the authenticity of that earlier glimpse never left him. He knew what few mystics know, that he did not need to violate the integrity of Reason, nor become lost in generally hazy gushy feelings, to know Infinity, which is the truth of Reality.
-- Notebooks Category 22: Inspiration and the Overself > Chapter 5 : Preparing for Glimpses > # 10
