There is a story told by Ken Thompson about how, in effort to bootstrap a compiler on a new system, Douglas McIlroy wrote out a compiler for TMG, in assembly, by hand on paper, because the teletype was busy or just slow; He then "fed the paper into the paper" which compiled the compiler, on paper, and then McIlroy typed this output into the teletype directly where it could be executed in memory on their new PDP-7, thus giving them a compiler for the TMG compiler language, which is a recursive compiler-compiler, which could be used to port everything else to the new PDP-7.

I heard this described, either by Ken or someone else who saw this, as the most impressive single feat of human intellect they had ever witnessed.