A growing market for ejiao—a gelatin made from donkey hide believed by practitioners of traditional Chinese medicine to increase libido and slow aging—has led to a global trade of millions of donkey skins each year. Asses are often kidnapped from rural African villages, where their labor is valued highly, then taken to markets and slaughtered for export. “The donkeys,” said a sanctuary manager while visiting a market in Tanzania, “are very stressed.”

In an 1846 math textbook from the Free Grammar School of King Edward VI, one exercise considers an exchange of 450 bags of potatoes for cash, 15 chests of oranges, and 185 bushels of carrots; the remainder is nuts. The question is posed: “How many bags of nuts did I receive?”

A thirteenth-century Song dynasty text about commerce describes dangers faced by pearl divers, who sometimes fell prey to “huge fishes, dragons, and other sea monsters” that would rip open their stomachs or bite off their feet. A pearl was considered most valuable if perfectly round; the test was “that it will not cease rolling about all day when put on a plate.” To avoid heavy export duties, foreign traders sometimes concealed pearls in canes or umbrella handles.

A Byzantine general of “ignoble descent” oversaw the building of Petra, on the Colchian coast, and set up an import monopoly. “They are robbing us of all our gold as well as of the necessities of life, using the fair name of trade,” locals complained, according to Procopius. “There has been set over us as ruler a huckster who has made our destitution a kind of business.”

Ottoman humorist Yusuf al-Shirbini of Egypt railed against unfair levies, referring to them as “things being called innovation.” Al-Shirbini quoted scripture: one who brings about “an innovation or provides accommodation for an innovator, upon him be the curse of God.”