Before resorting to a paper clip, the trick was to reboot while holding the mouse button. This still works today with CDs if the CD is damaged and the OS gets caught up trying to read it.

I actually remember frantically searching through my uncle's Mac manual after I inserted a corrupt boot disk (or possibly not a boot disk at all) and then couldn't get the thing to boot, which meant I couldn't use the soft eject.

Fortunately the paperclip trick was in there.