1606
The mission that turned inland
For sixty years more the faith kept to the shore. Christianity, one historian wrote, lay entrenched without the walls of India. Then, on 10 November 1606, a small party rode out of Tuticorin for Madurai, and among them was a Roman nobleman's son named Roberto de Nobili. He found every door closed to him until he put off his European dress and took up the life of a sannyasi — one who resigns or abandons all. He learned Tamil and Sanskrit, ate once a day, and was let in. The inland mission he opened was passed down from one man to the next, and in 1683 it came into the hands of a Portuguese Jesuit of the royal household at Lisbon: John de Britto. From Madurai, de Britto came south.
What this source establishes
That before de Nobili, Christianity in India was held to the coast — "entrenched without the walls". Cronin is a modern biography, not a primary document, and he is still in copyright, so we quote him and do not reproduce his page.