Chinese vegetarianism, which is closely associated with Buddhism, in fact preceded the spread of Buddhism into China during the 1st century ad. Vegetarianism had been formulated during the Zhou dynasty (11th century–221 BC) as a means for rulers to prepare themselves spiritually before they were considered fit to make sacrifices to heaven or to their ancestors. As abstinence was a prerequisite to achieving this state of purity, several days prior to the major events rulers would stay in seclusion, away from their wives and concubines, refrain from eating meat and drinking wine, and instead undergo ritual ablutions and eat only vegetables and grain foods. Unfortunately, there is no detailed information on the vegetarian dishes they ate.