The Neanderthal didn’t know the word cylinder when he pulled one from the swamp. It was hard and light and he found a thousand usages for it. When he looked into it, the crystalline interior sparkled like heaven in the rain.
He gave it to his son, who passed it to his. It was lost and found a dozen times through the ages, resting finally behind climate-controlled glass, a light shining through its crystalline core.
Marcus saw the cylinder at the museum while wrestling with an intractable problem. His brain shouted “Eureka!”
He ran home and finished his time machine.