Messages in bottles are usually welcome finds on the beach, but a variation steeped in superstition and witchcraft is being found along the Gulf Coast along Texas.

The “witch bottles” — created to thwart evil spells — are being collected by the Harte Research Institute for Gulf of Mexico Studies, and staff are making a point of leaving them unopened.

That’s because “witch bottles” are the result of old-school spell casting, and studies have revealed such strange contents as iron nails, rusty pins, hair and urine.

It’s suspected the bottles found along Texas originated in the Caribbean and South America, according to Jace Tunnell of the Harte Research Institute for Gulf of Mexico Studies.

“I’ve found around eight of these bottles and never opened one. I have five of them on my fence in the backyard since my wife won’t let me bring them inside,” he told McClatchy News.

“I don’t believe they are coming from the U.S., although I can’t be 100% sure since there is never any writing or indication of where they come from. However, we do find items washing up from all over the world due to the ocean currents, and sometimes I find these bottles in debris that contains distinct yellow vinegar bottles that originate from Haiti.”

“Witch bottles,” also known as “spell bottles,” are intended to “draw in and trap harmful intentions directed at their owners,” Tunnell says.

Hundreds of examples have been found buried or hidden in walls in the United Kingdom, according to a report by the McGill University Office for Science and Society.

“Back in the sixteenth and seventeenth centuries there was a powerful belief in witches and their ability to cause illness by casting a spell,” the society reports.

“But the evil spells could be fended off by trapping them in a ‘witch bottle,’ which if properly prepared, could actually reflect the spell itself while also tormenting the witch leaving the witch with no option but to remove the spell allowing the victim to recover.”

Believers thought opening the bottle would end protection for the creator and unbind the witch, according to a study published by the National Library of Medicine.

Standard ingredients might include urine “from either the afflicted person or an animal,” along with “pins, nails and human hair,” the library says. If buried, the preferred location was “in a dung hill.”

Bottles found by Tunnell appear to contain mostly herbs, “sticks and leaves.”

The Harte Research Institute, which is affiliated with Texas A&M University-Corpus Christi, has been combing beaches as part of a project to raise awareness of what is washing up out of the Gulf.

Tunnell’s beach finds have included a lot of traditional messages in bottles and such oddities as empty life pods, sea creature bones and cargo from a German ship “sunk by the US off the coast of Brazil in WWII 1944.”