On Christmas Day, I watched a documentary about the terra cotta warriors — thousands of clay soldiers built as funerary objects for the tomb of Qin Shi Huang, China's first emperor. One crazy fact I learned: Unlike the type of lacquer we call shellac today (which comes from crushed beetles), ancient Chinese artists used a lacquer derived from the sap of the lacquer tree, a relative of poison ivy. Anybody tasked with the job of applying that lacquer can end up with a serious allergic reaction. Another fun fact: We've still never seen the inside of Qin Shi Huang's tomb. Partly, this is a bureaucratic issue. But the larger problem is the mercury-laden soil on top, possibly contaminated by Qin Shi Huang's tomb, itself, which was supposed to contain a scale model of his empire, complete with rivers and oceans flowing with (you guessed it) mercury.