mexican archaeologist found mercury in chamber of teotihuacan pyramid .
the chamber had been sealed at the end of a tunnel for nearly 1,800 years .
because of the potential supernatural significance of liquid mercury in rituals , archaeologist sergio gomez hopes to find king 's tomb in pyramid .
teotihuacan , or ` abode of the gods ' in the aztec language of nahuatl , was distinct from the mayan civilization .