Each March, according to Roman antiquarian sources, the Vestal Virgins and other officiants made twenty-seven puppets from rushes, bound and shaped roughly like men, and distributed them among shrines called Argei scattered across Rome's districts. Two months later, on the Ides of May, these same effigies were gathered up, carried in procession by the pontifices and Vestals to the Pons Sublicius, Rome's oldest bridge, and thrown into the Tiber below. Ancient sources agree the rite had something to do with purification of the city, the sort of ritual cleansing Roman religion regularly performed at fixed points in the calendar, but they diverge sharply on what the puppets themselves represented and why throwing bound human figures into the river should achieve that end.
The Vestals' central role and the rite's clear connection to two of Rome's most archaic religious institutions, the bridge itself and the college of Vestals, mark it as very old, likely reaching back to the earliest strata of Roman religious practice, well before the historical explanations later writers offered for it had settled into anything like consensus. Twenty-seven such shrine-stations eventually stood across the city's districts, and Roman antiquarians disputed whether the number reflected an old Romulean division of the city or a later reorganization, a question left as unresolved as everything else about the rite's deeper meaning.