The chief source of the food supply was agriculture. Maize was the principal crop, and the arable land was carefully let out to families by the heads of the villages. Beans and peppers were also cultivated and bees were domesticated, from which both honey and wax, used in various arts, were collected. Cotton was woven into fabrics of such delicacy that the Spaniards at first thought the stuffs were of silk. It was dyed of many colors, and was the main material of clothing. Brilliant feathers were highly prized. Their canoes were seaworthy, and though there was no settlement of the Mayas on the island of Cuba as has been alleged, there was a commercial interchange of products with it, since Columbus was shown wax from Yucatan and was told about the peninsula. An active commerce was also maintained with southern Mexico, along the Gulf Coast, the media of exchange being cacao beans, shells, precious stones and flat pieces of copper.[207] The points which have attracted the most attention in Maya civilization, next to its architecture, are the calendar and the hieroglyphics. The calendar is evidently upon the same basis as that of the Mexicans, turning upon the numerals thirteen, twenty, and four. But the Mayas appear to have had more extended measures for the computation of time than the Aztecs. Besides the cycle of twenty years, called by them the _katun_, and that of fifty-two years, they had the _ahau katun_, or Great Cycle, of two hundred and sixty years. Both the Cakchiquels, Quiches and Mayas of Yucatan were literary peoples. They made frequent use of tablets, wrote many books, and covered the walls of their buildings with hieroglyphs carved on the stone or wood, or painted upon the plaster. Their characters are entirely different from those of the Mexicans. Most of them have rounded outlines, something like that of a section of a pebble, and for this reason the name “calculiform” has been applied to the writing. Their books were of maguey paper or of parchment, folded like those of the Mexicans. Although five or six of them have been preserved, as well as numerous inscriptions on the walls of buildings, no satisfactory interpretations have been offered, largely, perhaps, because none of the interpreters have made themselves familiar with the Maya language.[208]