Mirrors and Scrying
A famous Elizabethan magician's obsidian scrying mirror was analysed geochemically in 2021 and shown to be Mexican obsidian, tying it to Aztec trade and a deity associated with smoking mirrors. The study proves where the stone came from; not that it was ever used in an Aztec ceremony before reaching England as looted material.
John Dee and Edward Kelley's scrying sessions (from 1582); a 2021 Antiquity geochemical study identifying Dee's mirror as Mexican obsidian
The practice of gazing into a polished surface to receive visions, using tools ranging from crystal balls to volcanic glass mirrors.