... [There is no] a greater prophet than John [the Baptist] ... I dont expect I can work Miracles enough to open greatest prophet. What constituted him.--no prophet, if do no miracles John did no miracles.
... instituted before the creation Devil could not come in sign of a dove.--Holy Ghost is a personage in the form of a personage --does not confine itself to form of a dove--but in sign of a dove....
John at that time was the only legal administrator holding the keys of Power there was on Earth.
[Source: Joseph Smith Diary, by Willard Richards, in The Words of Joseph Smith by Joseph Smith by Andrew F. Ehat and Lyndon W. Cook]