Preserving Mesa, the Xerox Star system programming language
The goal of this project is to preserve and present primary and secondary source materials (including specifications, source code, manuals, and papers discussing design and implementation) from Mesa, the system programming language designed at Xerox PARC in the 1970s and used to implement the Xerox Star office automation system and its follow-ons. The editor greatly appreciates comments, suggestions, and donations of additional materials.Wikipedia has a short overview of Mesa, and here's the 1979 Mesa Language Manual, which is obviously a lot more in-depth.