Thanks for clarifying, Laurie - wow, what an honor for U. Grant!!! (Speaking of handshaking-taboos, didn't Mrs. Obama undergo a faux pas in this regard when meeting the Queen?)
Here's a follow-up question to the follow-up question. One president addressed the Emperor of Japan in a letter as follows (quite casually IMO):
"Great and Good Friend:
...
Wishing abundant prosperity and length of years to the great State over which you preside, I pray God to have Your Majesty always in His safe and holy keeping.
Written at the City of Washington... Your Good Friend,???"