Doug Engelbart's copy of As We May Think - with Doug's 1962 notes scribbled in the margins
The Doug Engelbart Foundation's 1995 Vannevar Bush Symposium video archive page includes a section on Bush's influence on Doug's work, including his copy of Bush's As We May Think with Doug's 1962 notes in the margins (pdf). Talk about deeply intertwingled living history. Per a note in the .pdf, the original hardcopy has apparently been donated to the Computer History Museum. Look for this paper when the Computer History Museum's Revolution - The First 2000 Years of Computing exhibit opens in Mountain View CA - and online on 13 Jan 2011.