The pornographic work by Twain might be 1601 (known by various
titles such as "A fireside conversation in Elizabethan Times),
although it is usually available in some edition or another.  The
second possibility is a book that was published 10 or 15 years
ago called (I think) The mammoth cod.  It is very likely out of
print.

Terry Ballard
Adelphi University