When archaeologists digging between busy lanes of traffic on Virginia’s Interstate 64 unearthed a broken bottle filled with nails, they weren’t sure exactly what they had found.

The glass vessel discovered at an old Civil War fortification east of Williamsburg might simply have been an ad hoc toolbox for troops garrisoned at the site nearly 160 years ago. But researchers at the Center for Archaeological Research at the College of William & Mary advanced a far more intriguing theory this week.

The artifact, they say, may in fact be a “witch bottle,” one of only a handful that have been found in the United States.

What’s a witch bottle? For centuries, they were used as occult countermeasures to the mischief of suspected sorceresses in England and America.

The evidence of a superstitious purpose is circumstantial but compelling, according to Joe Jones, the center’s director.