Young ladies! Are you wondering about the names of your future husbands? Wonder no more! Your prospects are written in strings of slimy, sticky exudates. Right. And all you need to attain this giddy piece of knowledge is a...snail (but definitely not a reptile).
George Benn explains it all in The History of the Town of Belfast, with an Accurate Account of Its Former & Present State; to which are added a Statistical Survey of the Parish of Belfast, and a Description of Some Remarkable Antiquities in its Neighbourhood (1823):
On May eve, when the sun has gone down, it is customary for young damsels to go forth to the fields in a body, when each of them procures a living snail or a bunch of yarrow, from either of which it is in their power to discover (by a method which has received the sanction of the most prudent and knowing matrons) the names of those who are to be their partners through this "breathing world." The process is simple. A dish or platter, whether of earthen ware or wood it matters not, is placed over the body of the unintelligent reptile, which has free liberty to exercise its nimbleness on an arena of meal or sawdust, the exact dimensions of the prison house in which it is thus most innocently incarcerated. Though the snail be not reckoned the most active of the animal creation, yet neither is it altogether disposed to a state of perfect quiescence, and as in all its movements it is well known to leave a shining "pledge behind," so in its rambles when in bondage during this critical night, the faculties of the creature are miraculously enlarged, and it is found to trace with singular precision some two or three letters of the Roman alphabet which form the initials of the name of some future happy helpmate.At the end, there is no questioning of the snail’s declaration.
If at any time, however, a mischievous or an incredulous person should have an opportunity of pointing out any superfluity in the inscription (a case not absolutely impossible), his objection is readily and justly obviated by claiming due allowance for the flourishes of so expert and tasteful a scribe.But don’t blame the poor snail if you one day end up with an unintelligent reptile for a husband.