One of the most solemn forms of oath taken on the eve of battle required a warrior to swear “by the shoulder of a horse and the edge of a sword” that he would not flee from the enemy even if the latter should be superior in strength.[153] At the time of the conquest of Peru, the Indian aborigines were amazed at the sight of the Spanish horsemen, believing that man and horse were one creature. And it is said that Pizarro owed his life to this superstitious belief; for on one occasion, when pursued by the natives, he fell from his horse, and the Peruvians who witnessed the mishap, believing that one animal had by magic divided itself into two, gave up the pursuit in dismay.[154] M. D. Conway, in his “Demonology and Devil-Lore,” asserts that the Scandinavian superstition known as the “demon-mare” is the source of the use of the horse-shoe against witches. In Germany there is a saying in reference to the morbid oppression sometimes experienced during sleep or while dreaming, and which is a symptom of indigestion, “The nightmare hath ridden thee.” This elvish mare rides horses also, and in the morning their manes are found all tangled and dripping with sweat. Grimm says that the traditional idea of the Nightmare seems to waver between the ridden animal and the riding, trampling one, precisely as the Devil is sometimes represented as riding men, and again as taking them on his back after the manner of a horse. According to a Bavarian popular belief, the Nightmare is a woman, who is wont to appear at the house-door of a morning, invariably requesting the loan of some article. In order to get rid of her at night, one should say: “Come to-morrow and receive the three white gifts.” The next morning the woman comes, and is given a handful of flour, a handful of salt, and an egg.[155] In the north of England, naturally perforated stones are hung up by the side of the manger to prevent the Night Hag from riding the horses. In a rare book of the sixteenth century, entitled “The Fower Chiefest Offices belonging to Horsemanship, by Tho. Blundenill, of Newton Flotman, in Norffolke,” the following curious charm is given as a remedy for horses affected with the nightmare:— Take a Flynt Stone that hath a hole of hys owne kynde, and hang it ouer hym and wryte in a bill: _In nomine patris_, etc. Saint George our Ladyes Knight, He walked day so did he night Until he hir found, He hir beate and hir bounde, Till truely hir trouth she him plyght That she woulde not come within the night. There as Saint George our Ladyes Knight Named was three tymes, Saint George. And hang this Scripture ouer him, and let him alone. With such proper charmes as thys is, the false Fryers in tymes past were wont to charme the money out of the playne folkes purses.