Alan Turing, known as the father of modern computing, explored new approaches and theories of mathematics in this journal.
Cassandra Hatton, senior specialist in Fine Books and Manuscripts and the History of Science at auction house Bonhams, holds Turing's notebook. Its "mathematical content gives an extraordinary insight into the working mind of one of the greatest luminaries of the 20th century," she said in a press release announcing the diary's sale.
Bonhams calls the diary "The hidden wartime manuscript by the father of computing." The notebook is expected to fetch at least $1 million when it goes up for sale in April.
It's rare to find anything with Turing's handwriting, because he usually typed his thoughts, Hatton said. With 56 pages written in Turing's own hand, the diary is the most extensive example ever found.
Turing wrote his mathematical notations between 1940 and 1942 while working at Bletchley Park to help break the codes generated by the Nazi's cipher machines, including Enigma.
Historians have written that the work at Bletchley Park helped to shorten World War II by two to four years.
The diary shows Turing found the time to pursue the analysis of pure mathematics, even while while working during the day to break codes.
Turing's exploration of mathematics led him to re-examine the work of his predecessors in hopes of learning from their mistakes.
He came up with the idea for a stored-program, electronic computing machine and the foundations of artificial intelligence.
On February 19, 1946, Alan Turing submitted his now famous "Proposal for the Development in the Mathematics Division of an Automatic Computing Engine" -- or ACE -- at a meeting of the National Physical Laboratory in England. It was a breakthrough: a design for a computer that could store both data and instructions in memory.
In 1950, National Physical Laboratory built the Pilot ACE. Among the world's first so-called stored-program computers, it used about 800 vacuum tubes and had a clock speed of 1MHz.
Before committing suicide in 1954, Turing willed all his manuscripts to friend and fellow mathematician Robin Gandy. Gandy used the blank pages in the middle of the notebook to keep an intimate dream journal.
Turing's "Proposal for Development in the Mathematics Division of an Automatic Computing Engine" was written during the era of this manuscript, and was the first relatively complete specification of an electronic stored-program general-purpose digital computer.
Turing's notebook is scheduled to be auctioned by Bonhams Fine Books & Manuscripts in New York on April 13, 2015. The notebook is expected to fetch at least $1 million.
Cassandra Hatton, senior specialist in Fine Books and Manuscripts and the History of Science at Bonhams, pages through the Turing manuscript in San Francisco on February 4, 2015.
A closer look at one of Turing's handwritten equations.
A stamp inside the cover reveals the notebook was purchased from a stationery shop on Trinity Street in Cambridge, England.
Turing's notebook is stored in a specially prepared protective case.
Called the father of modern computing, Turing is now the subject of "The Imitation Game," starring Benedict Cumberbatch and Keira Knightley, which is based on the biography "Alan Turing: The Enigma," by Andrew Hodges.
After the war, Turing was sentenced to chemical castration after being found guilty of crimes of gross indecency for engaging in homosexual acts. He committed suicide in 1954 as a consequence of that treatment.