He cited two historical examples illustrating interconnected economic systems with forms of currency that were transported: Pre-Columbian Western North America used shell beads, and Western Europe employed bronze or copper ingots. Both established trade routes that crossed great distances.
In both cases, goods were traded across “numerous cultural, linguistic, and political boundaries.” He emphasizes that the chance of meeting again was uncertain, reducing the possibility of delaying payment. There was a need to exchange valuables efficiently at the moment.