5MB and it ran SLS! I even managed to run X11 and emacs (xemacs I think?), although it was very much a matter of either running X11+emacs or compiling but not both.
3 megs RAM and SLS Linux here, around 1993. This was a 386SX laptop with 1 meg onboard and a 2 meg expansion. X11 barely ran and I didn't dare try emacs, so I had to learn vi.