Until about 100 years ago, when modern geology revealed its prevalence, salt was one of the world's most sought-after commodities. A substance so valuable it served as currency, salt has influenced the establishment of trade routes and cities, provoked and financed wars, secured empires and inspired revolutions.

"On a cool June evening in 2009, after performing a concert at London's Royal Academy of Music, twenty-year-old American flautist Edwin Rist boarded a train for a suburban outpost of the British Museum of Natural History. Home to one of the largest ornithological collections in the world, the Tring museum was full of rare bird specimens whose gorgeous feathers were worth staggering amounts of money to the men who shared Edwin's obsession: the Victorian...