The looking-glass is often turned with the face to the wall, or taken out of the room during a thunder-storm, because “quick-silver is so bad to draw the lightning.”
Bathurst, N. B.

The looking-glass is often turned with the face to the wall, or taken out of the room during a thunder-storm, because “quick-silver is so bad to draw the lightning.”
Source: Current Superstitions (1896), entry 1408.
Fanny D. Bergen, editor.
Modern normalized navigation; the historical attribution above remains unchanged.