The Unix Programmer's Manual, 1st ed. [1971]

Here's everything: http://cm.bell-labs.com/cm/cs/who/dmr/1stEdman.html

HTML-ized version of the 1st ed. manual: http://man.cat-v.org/unix-1st/

(Which works as mirror, given that the Bell Labs site seems to have crashed under the weight of the news of dmr's dead)