Alan Turing, Engima-breaking mathematician and Benedict Cumberbatch lookalike, never wrote much during his life -- manuscripts and diaries are hard to come by. The best remaining example was a 56-page notebook working on "the foundations of computer science", which has sold at auction for $US1,025,000.
The original Bonhams press release on the auction boasted a sale estimate of "at least seven figures", so the auction house only narrowly avoided embarrassment thanks to a mysterious bidder. A portion of the proceeds will be donated to charity.
The notebook was passed to Turing's friend and mathematician, Robin Oliver Gandy following Turing's death. Gandy used the central pages of the journal as a dream journal for a time, and as such the notebook was never included in the publicly accessible Turing Archive, and was never seen (or heard of) until the recent auction. [Bonhams]