About 2,000 years ago, a Roman emperor named Nero sent his servants on a mission to find a treasure that was prized throughout the world. This mission would take the men through treacherous mountains, pitting them against avalanches, thieves, and wolves . They weren't gold or silver that the men sought: It was ice.

Today, ice is so common you likely don't notice them clinking in your glass of lemonade. Thanks to the freezer you have in your kitchen, you can make as many ice cubes as you like and keep food frozen for long periods. But until the 1850s, ice was rare and precious.

To get ice, you had to do what Emperor Nero did: Find it in nature and haul them back home. Teams of men (often slaves) would be sent to gather ice from a blustery