The earliest references to Sindhi literature are contained in the writings of Arab historians; Sindhi was among the earliest Eastern languages into which the Quran was translated in the eighth or ninth century AD. Evidence exists that Sindhi poets recited verses before Muslim caliphs ruled in Baghdad. Secular treatises were also written in Sindhi about astronomy, medicine, and history during the eighth and ninth centuries. Pir Nooruddin, an Ismaili missionary who lived in Sindh in 1079, wrote Sufi poetry in the Sindhi language. His verses, known as "ginans", are an example of early Sindhi poetry. Because Pir Nooruddin was a Sufi and an Islamic preacher, his verses are full of references to (and descriptions of) mysticism and religion.