Dear RHH,

     Thank you very much.

     This certainly does seem the best supported and most likely of
the hypotheses.  And, as I remember the expression on Twain's face,
it seems a bit more pained than amused.  Of course, such an
expression could be used as part of a joke, but it is more likely to
indicate uncomfortable compliance with an undeniable request, exactly
the sort of response any of us might have to a sculptor who asked us
to get cold and uncomfortable for a while.