_More Maxims of Mark_, published by Merle Johnson in 1927 is the only
source for a number of specific Twain quotes. Johnson, at one time,
had access to a number of Clemens's unpublished journals and other
writings.  Tracking the originals that were once in Johnson's
possession and verifying them is a project that I don't believe
has ever been fully undertaken.  Some of the collectors or other
editors on the Forum may be able to offer you more insight into a
number of the activities Merle Johnson was involved in and how
he conducted his business.

Barb