Prince Rupert’s drop
A solid, hollow glass object, about two inches long, with a bulbous end and a narrow, curving “tail.” It is made by dropping a blob of hot glass into cold water and leaving it there until it has cooled. The rounded end resists a blow, but because of internal stress due to the absence of annealing, the tail shatters into numerous fragments if it is broken or scratched. These objects, which have aroused great curiosity, were introduced into England by Prince Rupert (1619-1682), nephew of Charles II . Samuel Pepys described them in his diary on January 13, 1662.