The Burgess Animal Book For Children in "Two Wonderful Mountain Climbers"

Ryder nodded, and Old Mother Nature went on. "Just imagine him with a smooth coat of grayish-brown instead of a white woolly one, and immense curling horns many times larger than those he now has.
Give him a large whitish or very light-yellowish patch around a very short tail. Then you will have a very good idea of one of those mountain climbers I promised to tell you about, one of the greatest mountain climbers in all the Great World Bighorn the Mountain Sheep, also called Rocky Mountain Bighorn and Rocky Mountain Sheep.