The upcoming holiday of Halloween may derive, in part, from the Celtic holiday of Samhain. But the Celts weren’t the only ones to appease their dead. In fact, the Romans did so on numerous festivals, including the Lemuria, a rite that Ovid traced back to the very founding of Rome. Who knew the spirits of Romulus and Remus still haunted their descendants?

The Lemuria took place on three different days in May.

On the ninth, eleventh, and thirteenth of that month, Roman householders gave offerings to their deceased ancestors to make sure their angry grandparents didn’t haunt them. The great poet Ovid - the man behind the "Metamorphoses" - chronicled Roman festivals in his "Fasti." In his section on the month of May, he discussed the Lemuria.

Ovid alleged that the festival got its name from “Remuria,” a festival named for Remus, Romulus’s twin brother whom he killed after founding Rome. Remus appeared as a ghost after his death and asked his brother’s friends to make future generations honor him. Said Ovid, “Romulus complied, and gave the name Remuria to the day on which due worship is paid to buried ancestors.” Eventually, “Remuria” became “Lemuria.” Scholars doubt that etymology, however, instead supporting the likely theory that Lemura was named for the “lemures,” one of several types of Roman spirits.

So how do you celebrate Lemuria? Take off your shoes, for one - you can’t have any knots on you.

Some scholars theorize that knots were forbidden to allow natural forces to flow properly. Then, walk around in your bare feet and make a sign to ward off evil, a gesture called mano fica. Next, scrub down in some fresh water and throw black beans (or take them into your mouth and spit them out over your shoulder), looking away and saying nine times, “These I cast; with these beans I redeem me and mine."

Why beans? Perhaps the souls of the dead reside in the legumes. By throwing away beans and what they symbolize or contain, you'd remove potentially dangerous spirits from your home. The ghosts are really into the beans, Ovid noted, so they’ll follow the food and leave you alone. Next, wash yourself and bang together some pieces of bronze from Temesa in Calabria, Italy. You'll ask the shades to leave your home nine times, saying, "Ghost of my fathers, go forth!" And you're done.

What kind of rite is this? It's not "black magic" as we think of it today, which Charles W. King explains in his essay “The Roman Manes: the Dead as Gods." If the Romans even had such a concept, it would have applied to “invoking supernatural powers to harm others,” which doesn't happen here. As King observes, the Roman spirits in the Lemuria aren't the same as our modern ghosts. These are ancestral spirits to be propitiated. They might harm you if you don’t observe certain rites, but they’re not necessarily inherently evil.

So who are the deceased of the Lemuria? Those spirits Ovid mentions aren’t all one and the same. One particular category of spirits is the manes, which King defines as the “deified dead”; in his "Roman Gods: a Conceptual Approach," Michael Lipka terms them “the venerable souls of the past.” In fact, Ovid calls the ghosts by this name (among others) in his "Fasti." These manes, then, aren’t just spirits, but a kind of god.

Such rituals as the Lemuria aren’t only apotropaic - representative of a type of magic to ward off negative influences - but also negotiate with the dead in different ways. In other texts, interaction between the human and the manes is encouraged. Thus, the Lemuria provides an insight into the complexities of the ways the Romans regarded their dead.                

But these manes aren't the only ghoulish guys involved in this festival. In Jack J. Lennon’s "Pollution and Religion in Ancient Rome," the author mentions another kind of spirit invoked in the Lemuria. These are the taciti inferi, the silent dead. Unlike the manes, Lennon says, “these spirits were labeled as harmful and malicious.” Perhaps, then, the Lemuria was an occasion to propitiate different kinds of gods and spirits all at once. Indeed, other sources say the gods worshippers placated at the Lemuria weren't the manes, but the lemures or the larvae, which were often conflated in antiquity. Even Michael Lipka terms these different types of spirits “confusingly similar.” So the Romans probably took this holiday as a time to appease all the ghost-gods.

Although Lemuria isn't celebrated today, it might have left its legacy in Western Europe. Some scholars theorize that modern All Saints’ Day derives from this festival (along with another ghostly Roman holiday, Parentalia). Though that assertion is a mere possibility, Lemuria still reigns supreme as one of the deadliest of all Roman holidays.