Actually, I've seen the small-round-to-big-round kind of table on a TV
antique show. I can definitely remember that the mechanism was
something like the overlapping plates of the old style camera shutters.
I do recall it started round and ended up round but do NOT ask me to
explain the mechanics. If I were as clever as the Victorian engineers
I'd have died 125 years ago.
FoggyTown
"Cut to shape . . . pound to fit."