A Greek kantharos, drinking vessel from the 1st century AD.
"The story is, that a ship, laden with nitre, being moored upon this spot [the river Belus], the merchants, while preparing their repast upon the sea-shore, finding no stones at hand for supporting their cauldrons, employed for the purpose some lumps of nitre which they had taken from the vessel. Upon its being subjected to the action of the fire, in combination with the sand of the sea-shore, they beheld transparent streams flowing forth of a liquid hitherto unknown: this, it is said, was the origin of glass."
Pliny the Elder - Naturalis Historia (the Natural History) XXXVI.65
Translated by J. Bostock and H.T. Riley