A quick tour through _Mark Twain Himself_ shows both left- and
right-handedness. To further confound us, one photo of Twain in bed shows
him with cigar in left hand and pen in right hand simultaneously!

This apparent ambidextrousness may have been intentionally developed: After
all, holding a cigar in one's left hand, while sitting on a porch, keeps
one's right hand free for petting any cats who might happen to be in the
vicinity. :-)

Best regards,

Mary Leah Christmas