In looking at the correspondence between Twain and his publishers including
those letters appearing in _Mark Twain, Business Man_, it appears that
the plates for _Library of Humor_ may have already been produced as
early as 1885.
Clemens wrote to Charles Webster on Jan. 23,1885, "My only objection, is
that the publisher may be sued for damages for using copyrighted matter
without obtaining consent....Not much danger of such a suit, but of course
there is some." (p. 294-95, _Mark Twain, Business Man_).
Apparently it was easier and cheaper to deal with Alexander Belford than to
excise 3 pages of Bill Nye from _Library of Humor_. Would be interesting
to see that exchange of letters, if they exist.