to decline for at least another 50 years after Toledo. A report to the king of Spain in the 1580s said that "many of the Indians have died in the mines, in other labors, or from the recurrent epidemics; others have fled to escape their labor and tribute obligations." Mining Mining, especially silver mining, was the most important economic enterprise of the Viceroyalty. A single mountain at Potosi in Bolivia produced an estimated 60% of all the silver mined in the world during the second half of the 16th century. A twenty percent tax on mining was a major source of revenue for the kingdom of Spain. Silver was mined at Potosí by Inca methods, but the purest silver was depleted by the 1560s and production declined. However, the Patio process, a new method of purifying silver ore using mercury, was invented in Mexico. Toledo confiscated the mercury mines at Huancavelica for the Spanish crown and introduced the Patio process. He called it "the most important marriage in the world between the mountain of Huancavelica and the mountain of Potosi." Between 1571 and 1575 production of silver quintupled. The increase in silver and mercury production resulted in a demand for thousands of laborers with much of the demand being filled by forced laborers. Potosi became one of the largest cities of the world with a population as large as London. Forced labor The most important objective of Toledo's reductions was to facilitate access to Andean labor, especially for the mines whose revenues were important to the finances of the mother country of Spain. Other measures He worked hard to convert the Indigenous and provide them with religious training. He tried to adapt the political and social structures of the Incas to life in the viceroyalty. He also used the old system of mita, which had been a form of corvée labour under the Incas, as a form of forced native labor. Under his reforms of the mita, no more than one seventh of the male population of a village could be conscripted, they could not be forced to work far from their native villages, and they were entitled to compensation for their labor. These reforms later were called the Toledo Reforms. Toledo assigned Pedro Sarmiento de Gamboa the task of writing a chronicle of prehispanic times in Peru by compiling information given by some of the older survivors from that