In ancient Greece, some mystics used mirrors as a form of fortune telling and divination, a practice called catoptromancy. These “mirror seers” would dip a looking glass into water before having a sickly person look into it. If the image was distorted, they were done for. If clear, all would be well.
To begin, it’s helpful to have some background on Samhain. In Celtic Ireland, around 2,000 years ago, Samhain represented the division between the lighter half of the year that was summer and the darker half that was winter. During the interim, ancient people believed that the line between the spirit world and the mortal one became so thin that the dead could pass through it and walk the earth once more.