A project has been created to recover first edition Unix, dated June 1972, exactly as specified in the Unix Programmer’s Manual of 3 November 1971.
Right now the kernel listing hosted on bitsavers, PreliminaryUnixImplementationDocument_Jun72 (pdf 12Mb), is being run on a slightly modified version of SIMH.
On its website we can read:
This project will create readable and compilable code from the printouts of the first edition of Unix from 1972. Many executable programs still exist in binary form and this project will try to restore an incomplete but functional first edition Unix system. The software will keep the copyright of the original authors, which is currently licensed freely under the Caldera ancient UNIX license.
For more information you can visit the unix-jun72 project page, or subscribe to the mailing list https://minnie.tuhs.org/mailman/listinfo/unix-jun72.
Update (07 – June – 2008):
The kernel of the 1st edition of Unix has been able to run again under SIMH. The only known version of the kernel was a printout that had to be scanned, then edited by hand, and finally debugged.
The kernel consists of 4200loc, written in PDP11 ASM, runs on a 24Kbyte machine and supports 8 concurrent users.
All this is very interesting for those interested in kernels, Unix, or the history of operating systems and computing, and it is within your reach on the project page linked above.