General Grant's horse - Glass negative photogrpah. Public domain.

Photo shows riderless horse at funeral procession on April 26, 1912, for Major General Frederick Dent Grant (1850-1912), son of President Ulysses S. Grant, former New York City Police Commissioner and commander for the Eastern Division of the U.S. Army. (Source: Flickr Commons project, 2008 and New York Times, April 24, 1912)