Ulysses S. Grant and R. Hayim Tzvi Schneerson

Smooth Stone published an account of a meeting between Rabbi Hayim Tzvi Schneerson, a grandson of the Alter Rebbe (and a grandson of the infamous Rav Maishe, see Schneersons in Australia post): He was received at the White House in 1869 by the newly inaugurated President Ulysses Grant.
(I believe the meeting was begrudgingly sponsored by R. A. Shemtov, who complained bitterly that Rabbi Hayim Tzvi Schneerson was not a real mekushar)