E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The touchstone of virtue, given to Alasnam by one of the Genii. If he looked in this mirror it informed him whether a damsel would remain to him faithful or not. If the mirror remained unsullied so would the maiden; if it clouded, the maiden would prove faithless.Arabian Nights: Prince Zeyn Alasnam.