L. Frank Baum's 1901 illustrated novel, The Master Key: An Electrical Fairy Tale, Founded Upon the Mysteries of Electricity and the Optimism of its Devotees, describes the adventures of a 15 year old boy who experiments with electricity and accidentally touches "the Master Key of Electricity," encountering a Demon who gives him various gifts. One of these gifts is a "Character Marker" introduced on p. 94:
"It consists of this pair of spectacles. While you wear them every one you meet will be marked upon the forehead with a letter indicating his or her character. The good will bear the letter 'G,' the evil the letter 'E.' The wise will be marked with a 'W' and the foolish with an 'F.' The kind will show a 'K' upon their foreheads and the cruel a letter 'C. Thus you may determine by a single look the true natures of all those you encounter."
This character marker has been viewed retrospectively as an early foreshadowing of features analogous to those obtainable in augmented reality devices.