Whilst the original French texts were unknown, the king here spoken of figured in the old Latin versions as King Darius, and in Ramusio as Re Dor.  It was a most happy suggestion of Marsden’s, in absence of all knowledge of the fact that the original narrative was French, that this Dor represented the Emperor of the Kin or Golden Dynasty, called by the Mongols Altun Khan, of which Roi D’Or is a literal translation.

Of the legend itself I can find no trace.  Rashiduddin relates a story of the grandfather of Aung Khan (Polo’s Prester John), Merghuz Boiruk Khan, being treacherously made over to the King of the Churche (the Kin sovereign), and put to death by being nailed to a wooden ass.  But the same author tells us that Aung Khan got his title of Aung (Ch. Wang) or king from the Kin Emperor of his day, so that no hereditary feud seems deducible.

Mr. Wylie, who is of opinion, like Baron Richthofen, that the Caichu which Polo makes the scene of that story, is Kiai-chau (or Hiai-chau as it seems to be pronounced), north of the Yellow River, has been good enough to search the histories of the Liao and Kin Dynasties,[1] but without finding any trace of such a story, or of the Kin Emperors having resided in that neighbourhood.

On the other hand, he points out that the story has a strong resemblance to a real event which occurred in Central Asia in the beginning of Polo’s century.

The Persian historians of the Mongols relate that when Chinghiz defeated and slew Taiyang Khan, the king of the Naimans, Kushluk, the son of Taiyang, fled to the Gur-Khan of Karakhitai and received both his protection and the hand of his daughter (see i. 237); but afterwards rose against his benefactor and usurped his throne.  “In the Liao history I read,” Mr. Wylie says, “that Chih-lu-ku, the last monarch of the Karakhitai line, ascended the throne in 1168, and in the 34th year of his reign, when out hunting one day in autumn, Kushluk, who had 8000 troops in ambush, made him prisoner, seized his throne and adopted the customs of the Liao, while he conferred on Chih-lu-ku the honourable title of Tai-shang-hwang ’the old emperor.’"[2]

It is this Kushluk, to whom Rubruquis assigns the role of King (or Prester) John, the subject of so many wonderful stories.  And Mr. Wylie points out that not only was his father Taiyang Khan, according to the Chinese histories, a much more important prince than Aung Khan or Wang Khan the Kerait, but his name Tai-Yang-Khan is precisely “Great King John” as near as John (or Yohana) can be expressed in Chinese.  He thinks therefore that Taiyang and his son Kushluk, the Naimans, and not Aung Khan and his descendants, the Keraits, were the parties to whom the character of Prester John properly belonged, and that it was probably this story of Kushluk’s capture of the Karakhitai monarch (Roi de Fer) which got converted into the form in which he relates it of the Roi d’Or.