Abstemius's Fables (Sir Roger L'Estrange)
339. (Abstemius 88) A Plain Horse wins the Prize.
There were a great many brave Sightly Horses with Rich Trappings that were brought out one Day to the Course, and only One Plain Nag in the Company that made sport for all the rest. But when they came at last to Trial, This was the Horse that ran the whole Field out of Distance, and Won the Race.
Our Senses are no competent Judges of the Excellencies of the Mind.
Fables of Aesop and Other Eminent Mythologists: Abstemius's Fables by Sir Roger L'Estrange. Available online at Google Books.