Mirrors could deter citizens from lying

Mirrors ‘reflect the image or face of a person... Mirrors capture, not the physical entity, but the double of a person, which may be the tonalli [life force/spirit] as an insubstantial shadow soul...
’If prehispanic Mesoamerican art is accurate, rulers, noblemen, and priests often wore mirrors in the form of shiny discs on their chests as pectorals [see image]. Anyone to whom they spoke was in danger of having his or her tonalli seized and perhaps even retained or injured during the interview. How could a petitioner lie, or a supplicant exaggerate when faced with the possibility of having his life force seized, manipulated, or even killed?’

Quote/info from The Natural History of the Soul in Ancient Mexico by Jill Leslie McKeever Furst, Yale University Press, 1995, p. 94.
Image: Mixtec ruler 11-Water wearing a mirror over her chest, Codex Zouche-Nuttall, fol. 26 (detail), scanned from our own copy of the ADEVA facsimile edition, Graz, Austria, 1987.