Joseph flees from Kirtland on his horse, "Old Charley," with Sidney Rigdon and rides 60 miles the first day. According to one story, a repentant apostate warns Joseph of a plot to assassinate him. The mob appears before Joseph can escape. He is quickly placed in a box nailed onto an ox cart. He is then driven out of town to safety, gets his horse, and rides off.
[Source: Conkling, Christopher J., Joseph Smith Chronology; Ivan J. Barrett, Joseph Smith and the Restoration 355]