In Twain's August 16, 1898 letter to Howells from Austria, it could be construed that he is forevisioning the smart phone and texting (although calling the future technology "mental telegraphy" and "mesmerizer-button").
If you do not have that letter handy, I have recorded it and posted it on YouTube (https://youtu.be/mLDxJuVOVy4) and on my facebook page (https://www.facebook.com/AdventuresOfMarkTwain/).

- B. Clay Shannon