THE SCENE: Marco Polo recounts a charming, and somewhat incredible, story about an Iranian King’s decision to experiment with the effect of soil on human temperament.
THE TEXT: Now let me tell you about an experiment that was made in the Kingdom of Kerman. It so happens that the people of this kingdom are good, even-tempered, meek, and peaceable, and miss no chance of doing one another a service. For this reason, the king once observed to the sages assembled in his presence: “Gentlemen, here is something that puzzles me, because I cannot account for it. How is it that in the kingdoms of Persia, which are such near neighbours of ours, there are folk so unruly and contentious that they are forever killing one another, whereas among us, who are all but one with them, there is hardly an instance of provocation or brawling?”
The sages answered that this was due to a difference of soil. So the king thereupon sent to Persia, and in particular to Isfahan aforementioned, who inhabitants outdid the rest in every sort of villainy. There, on the advice of his sages, he had seven ships loaded with earth brought to his own kingdom. This earth he ordered to be spread out like pitch over the floors of certain rooms and then covered with carpets, so that those who entered should not be dirtied by the soft surface. Then a banquet was served in these rooms, at which the guests had no soon partaken of food than one began to round on another with opprobrious words and actions that soon led to blows. So the king agreed that the cause did indeed lie with the soil.
– The Travels of Marco Polo, 14th Century AD