In some sense, you might consider it to be a crude one. If you configure your computer to boot directly into full screen emacs, never leave it, and do your damndest to interact only with in-process elisp, you might get some feel for what such a machine could be like.

It will also be a frustrating experience, since emacs was never really intended to be used in such a way. There’s going to be a lot of friction and limitations. Still, it’s a fun exercise for the right sort of person :)