I have five machines on 10.13.1 High Sierra (including two that aren't officially supported by it), but I just fired up my 1.07 GHz G4 iBook with 1.25 GB RAM and ATA hard drive, running 10.4.11, just because.
I had forgotten just how fast this thing boots up. Really quite quick. Unfortunately, it's very slow at anything else. Even just surfing MacRumors is painful.