GoKawiilRetro-computing writeup details early LISP systems running in tiny memory footprints
The piece traces LISP implementations that fit within extremely small memory budgets, starting with the original 1960 LISP on MIT's IBM 704, which used 32K words of 36-bit core with the LISP system itself taking 12K words, leaving under 20K cons cells. It also cites 1964's PDP-1 LISP, which ran on systems with just 4096 words of 18-bit storage, with the system consuming roughly 2000 words.