pyrite, a material used for making mirrors; the stone for making mirrors (see Molina and Karttunen)
IPAspelling:
petstɬi
Alonso de Molina:
petztli. piedra de espejos. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 81r. col. 2. Thanks to Joe Campbell for providing the transcription.
Frances Karttunen:
PETZ-TLI pl: -MEH pyrite, material used in making mirrors / piedra de espejos (M) [(1)Tp.225]. See PETZOĀ. Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 193.