Archaeologists excavated 10 wooden braziers (bowls that held hot coals) from the Jirzankal Cemetery at the western edge of China. The cemetery sits on the Pamir Plateau, a cultural center connecting India, China, and Persia that would later become a crucial stop on the Silk Road. Previous excavations in the area had already found remnants of cannabis. Knowing this, the study's researchers performed an analysis on the burnt traces of cannabinoids left on the braziers and found high concentrations of CBN, the chemical signature left behind by the burning of THC, on all but one of them. That provided what Spengler called "unequivocal evidence" of psychoactive cannabis smoking in this cemetery.