This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
The Saint Thomas Christians of the Malabar Coast had been Christian for well over a thousand years by the time Archbishop Aleixo de Menezes arrived to reform them in 1599, tracing their community's founding to the apostle Thomas himself and maintaining, across all that time, liturgical and ecclesiastical ties to the East Syriac Church of the East rather than to Rome. Menezes did not see a Christian community with a different history. He saw a community whose bishops and texts, connected to a church long labeled Nestorian in the West, needed correcting.
The Synod he convened at Udayamperoor did the correcting itself. Over six days, it revised the community's liturgy along Latin lines, formally condemned a list of existing texts and practices as tainted by heresy, and placed the entire community under a Latin bishop answering to Rome rather than to its own East Syriac hierarchy. The published acts of the Synod describe this as something the Saint Thomas Christian delegates themselves agreed to. The community's own remembered history, carried forward long after in ways the official record does not, describes considerably more pressure behind that agreement than the acts admit.
What the Synod could not fully erase was memory, and memory is what eventually answered it. More than fifty years later, in 1653, a large portion of the community gathered at a leaning stone cross in Kochi and swore never again to submit to Portuguese Jesuit authority, an event still remembered as the Coonan Cross Oath. The break it produced still shapes the Saint Thomas Christian churches of India today, most of which trace their present divisions back to exactly the rupture Diamper was meant to prevent.