Black pepper
The "Periplus" reveals how Muziris became the main trade port for the Chera chiefdom. The author explains that this large settlement owed its prosperity to foreign commerce, including shipping arriving from northern India and the Roman empire. Black pepper from the hills was brought to the port by the local producers and stacked high in warehouses to await the arrival of Roman merchants. As the shallows at Muziris prevented deep-hulled vessels from sailing upriver to the port, Roman freighters were forced to shelter at the edge of the lagoon while their cargoes were transferred upstream on smaller craft.