He rode an Arab horse
That King Darius had sent him. […]
You could not name the price of this horse,
Because he was so swift, and knew how to spin on his heels.
His back was two colours:
On one side he was white as an ermine,
On the other, black as a mulberry.
Nobody in the world could run beside him.
You can be sure, there was no other
So agile, be they bay or brown.
And he swiftly outstripped the brown and bay, left them flatfooted.
You would have to be mad to want a faster mount.

From the French version of the medieval poem, Roman des Thèbes. My (free) translation. All faults my own.