Warton, in his History of English Poetry, took much pains to gather together some information on the subject, and his remarks are therefore quoted here, nearly at length, for the reader's convenience. I omit most of his references.
'The Canterbury Tales,' says Warton, 'are unequal, and of various merit. Few perhaps, if any, of the stories are the invention of Chaucer. I have already spoken at large of the Knight's Tale, one of our author's noblest compositions. That of the Canterbury Tales which deserves the next place, as written in the higher strain of poetry, and the poem by which Milton describes and characterises Chaucer, is the Squire's Tale. The imagination of this story consists in Arabian fiction engrafted on Gothic chivalry. Nor is this Arabian fiction purely the sport of arbitrary fancy: it is in great measure founded on Arabian learning. Cambuscan, a King of Tartary, celebrates his birthday festival in the hall of his palace at Sarra with the most royal magnificence. In the midst of the solemnity, the guests are alarmed by a miraculous and unexpected spectacle: the minstrels cease on a sudden, and all the assembly is hushed in silence, surprise, and suspense; see ll. 77-88.
'These presents were sent by the King of Arabia and India to Cambuscan, in honour of his feast. The Horse of Brass, on the skilful movement and management of certain secret springs, transported his rider into the most distant region of the world in the space of twenty-four hours; for, as the rider chose, he could fly in the air with the swiftness of an eagle: and again, as occasion required, he could stand motionless in opposition to the strongest force, vanish on a sudden at command, and return at his master's call. The Mirror of Glass was endued with the power of shewing any future disasters which might happen to Cambuscan's kingdom, and discovered the most hidden machinations of treason. The Naked Sword could pierce armour deemed impenetrable, "were it as thikke as is a branched ook" (l. 159); and he who was wounded with it could never be healed, unless its possessor could be entreated to stroke the wound with its edge. The Ring was intended for Canace, Cambuscan's daughter, and while she bore it in her purse, or wore it on her thumb, enabled her to understand the language of every species of birds, and the virtues of every plant.
'I have mentioned, in another place, the favourite philosophical studies of the Arabians. In this poem the nature of those studies is displayed, and their operations exemplified: and this consideration, added to the circumstances of Tartary being the scene of action, and Arabia the country from which these extraordinary presents are brought, induces me to believe this story to be identical with one which was current at a very ancient date among the Arabians[[145]]. At least it is formed on their principles. Their sciences were tinctured with the warmth of their imaginations, and consisted in wonderful discoveries and mysterious inventions.
'This idea of a Horse of Brass took its rise from their chemical knowledge and experiments in metals. The treatise of Jeber, a famous Arab chemist of the middle ages, called Lapis Philosophorum, contains many curious and useful processes concerning the nature of metals, their fusion, purification, and malleability, which still maintain a place in modern systems of that science. The poets of romance, who deal in Arabian ideas, describe the Trojan horse as made of brass. These sages pretended the power of giving life or speech to some of their compositions in metal. Bishop Grosseteste's speaking brazen head, sometimes attributed to Roger Bacon, has its foundation in Arabian philosophy. In the romance of Valentine and Orson, a brazen head fabricated by a necromancer in a magnificent chamber of the castle of Clerimond, declares to those two princes their royal parentage. We are told by William of Malmesbury that Pope Sylvester II, a profound mathematician who lived in the eleventh century, made a brazen head, which would speak when spoken to, and oracularly resolved many difficult questions. Albertus Magnus, who was also a profound adept in those sciences which were taught by the Arabian schools, is said to have framed a man of brass, which not only answered questions readily and truly, but was so loquacious, that Thomas Aquinas, while a pupil of Albertus Magnus, and afterwards an Angelic doctor, knocked it in pieces as the disturber of his abstruse speculations. This was about the year 1240. Much in the same manner, the notion of our knight's horse being moved by means of a concealed engine corresponds with their pretences of producing preternatural effects, and their love of surprising by geometrical powers. Exactly in this notion, Rocail, a giant in some of the Arabian romances, is said to have built a palace, together with his own sepulchre, of most magnificent architecture and with singular artifice: in both of these he placed a great number of gigantic statues or images, figured of different metals by talismanic skill, which in consequence of some occult machinery, performed actions of real life, and looked like living men. We must add that astronomy, which the Arabian philosophers studied with a singular enthusiasm, had no small share in the composition of this miraculous steed. For, says the poet,
"He that it wroughte coude ful many a gin;
He wayted many a constellacioun,
Er he had doon this operacioun." (ll. 128-130.)
'Thus the buckler of the Arabian giant Ben Gian, as famous among the Orientals as that of Achilles among the Greeks, was fabricated by the powers of astronomy; and Pope Sylvester's brazen head, just mentioned, was prepared under the influence of certain constellations.
'Natural magic, improperly so called, was likewise a favourite pursuit of the Arabians, by which they imposed false appearances on the spectator.... Chaucer, in the fiction before us, supposes that some of the guests in Cambuscan's hall believed the Trojan horse to be a temporary illusion, effected by the power of magic (l. 218)....