On this date Twain and Cable were in Lowell, MA for a show at Huntington
Hall.  The day before they were in Melrose, MA, but there is a letter
from Twain to Pond dated November 11, 1884 from Boston, MA.  Given their
geographic locations, it doesn't make much sense to me for Sam Clemens
to be in Boston on that date to post a letter.  This is listed in MTP