More on King Chosen by the Neighing of a Horse from Infoplease:

• King Chosen by the Neighing of a Horse - King Chosen by the Neighing of a Horse (A). Darius. (See Horse : A horse wins a kingdom.) Source: ...
• Dictionary of Phrase and Fable: K - Definitions, origins, and illustrative excerpts for words, phases, and literary allusions starting with "K"