Two centuries after the French people beheaded Louis XVI and dipped their handkerchiefs in his blood, scientists believe they have authenticated the remains of one such rag kept as a revolutionary souvenir.

Researchers have been trying for years to verify a claim imprinted on an ornately decorated calabash that it contains a sample of the blood of the French king guillotined in Paris on January 21, 1793.

The dried, hollowed squash is adorned with portraits of revolutionary heroes and the text: "On January 21, Maximilien Bourdaloue dipped his handkerchief in the blood of Louis XVI after his decapitation"....