On his long road to the court of the Great Khan, the Franciscan John of Montecorvino halted for months near Mylapore around 1291 and buried a travelling companion beside the reputed tomb of the apostle Thomas. His letters give one of the earliest Latin descriptions of the Coromandel coast and its Christians — written by the friar who would go on to become the first Catholic archbishop in China.
Montecorvino's own letters (Yule, Cathay and the Way Thither) — public domain.
Sources & further reading