Pochteca (singular pochtecatl) were professional, long-distance traveling merchants in the Aztec Empire. The trade or commerce was referred to as pochtecayotl. Within the empire, the pochteca performed three primary duties: market management, international trade, and acting as market intermediaries domestically. They were a small but important class as they not only facilitated commerce, but also communicated vital information across the empire and beyond its borders, and were often employed as spies due to their extensive travel and knowledge of the empire. The pochteca are the subject of Book 9 of the Florentine Codex (1576), compiled by Bernardino de Sahagún. Pochteca occupied a high status in Aztec society, below the noble class. They were responsible for providing the materials that the Aztec nobility used to display their wealth, which were often obtained from foreign sources. The pochteca also acted as agents for the nobility, selling the surplus tribute that had been bestowed on the noble and warrior elite and also sourcing rare goods or luxury items. The pochteca traded the excess tribute (food, garments, feathers and slaves) in the marketplace or carried it to other areas to exchange for trade goods. Due to the success of the pochteca, many of these merchants became as wealthy as the noble class, but were obligated to hide this wealth from the public. Trading expeditions often left their districts late in the evening, and their wealth was only revealed within their private guildhalls. Although politically and economically powerful, the pochteca strove to avoid undue attention. The merchants followed their own laws in their own calpulli, and venerating their god, Yacatecuhtli, "The Lord Who Guides" and Lord of the Vanguard an aspect of Quetzalcoatl. Eventually the merchants were elevated to the rank of the warriors of the military orders. The pochteca were organized into powerful guilds, each based in one of the urban centers of the Valley of Mexico: Tenochtitlán Tlatelolco Huitzilopochco Cuautitlán Azcapotzalco Mixcoac Texcoco Huexotla Coatlichan Otompan Xochimilco Chalco Tlacopan Pochtecatl were based in thirteen urban centers in the Valley of Mexico.