The sea had its honour on the 16th of Boedromion. Since dawn, the city resounded with the cry “Alade mystai” (To the sea, mystai) as the heralds invited the prospective mystai to be cleansed in the ocean. The walk to the coast was known as Elasis. Each initiate was accompanied by his mystagogos and carried a piglet, which was also to be cleansed. The nearest beach to the city was the east side of Faliron or the Piraeus peninsula. The initiates probably used carriages to take them to the beach under the watchful eye of the epimeletes. The mystai entered the water with their piglets in a process of physical cleansing and spiritual purification. It was a solemn and austere ritual, which, however, was not always completely safe. Plutarch mentions the case of an initiate who was taken by a “big fish” (perhaps a shark?) and drowned while participating in the purification ritual in 339 BCE.

The would-be mystai then returned to Athens and sacrificed the animals. Ancient commentators have suggested various interpretations of the choice of piglets, including the view that their breeding was economical and accessible to all classes of mystai. More probable, however, seems to be the interpretation of the equation of unclean pigs with evil spirits but also their choice due to their proverbial fertility, which is the pre-eminently desired result of agricultural cults. The pig's blood absorbed the unclean spirit inhabiting human beings. It was a personal act, and each initiate had to sacrifice his own piglet. 

Figurine of Demeter with pig, 5th century BCE, sculpture, The Cleveland Museum of Art © The Cleveland Museum of Art