According to Hindu legend, the greater part of Sri Lanka was conquered in prehistoric times by Ramachandra, the seventh incarnation of the supreme deity Vishnu. The written history of the country begins with the chronicle known as the Mahavamsa. This work was started in the 6th century AD and provides a virtually unbroken narrative up to 1815. The Mahavamsa was compiled by a succession of Buddhist monks. Sinhalese society, although Buddhist, is stratified along caste lines. About 74 percent of the population of Sri Lanka is of Sinhalese descent. The largest minority groups are the Sri Lankan Tamils and the Indian Tamils, which together account for about 18 percent of the population.