(p.The book was written by romance writer Rustichello da Pisa, who worked from accounts which he had heard from Marco Polo when they were imprisoned together in Genoa.

Every man of rank or wealth has one in his house for his own use and the stock of wood must soon prove inadequate to such consumption whereas these stones may be had in the greatest abundance, and at a cheap rate. It is true there is no scarcity of wood in the country, but the multitude of inhabitants is so immense, and their stoves and baths, which they are continually heating, so numerous, that the quantity could not supply the demand for there is no person who does not frequent the warm bath at least three times in the week, and during the winter daily, if it is in their power. These stones do not flame, excepting a little when first lighted, but during their ignition give out a considerable heat. When lighted, it burns like charcoal, and retains the fire much better than wood inso- much that it may be preserved during the night, and in the morning be found still burning. Throughout this province there is found a sort of black stone, which they dig out of the mountains, where it runs in veins.

With it, in short, every article may be procured. All his subjects receive it without hesitation, because wherever their business may call them, they can dispose of it again in the purchase of merchandise they may have occasion for such as pearls, jewels, gold, or silver. When thus coined in large quantities, this paper currency is circulated in every part of the grand khan’s dominions nor dares any person, at the peril of his life, refuse to accept it in payment. The coinage of this paper money is authenticated with as much form and ceremony as if it were actually of pure gold or silver for to each note a number of officers, specially appointed, not only subscribe their names, but affix their signets also and when this has been regularly done by the whole of them, the principal officer, deputed by his majesty, having dipped into vermilion the royal seal committed to his custody, stamps with it the piece of paper, so that the form of the seal tinged with the vermilion remains impressed upon it, by which it receives full authenticity as current money, and the act of counterfeiting it is punished as a capital offence.

The Travels by Marco Polo