Wikipedia
Carromancy (from Greek carro, 'waxen', and manteia, 'divination'), otherwise known as ceromancy, is a form of divination involving wax. One of the most common methods of carromancy is to heat wax until molten, then to pour it directly into cold water. The shapes and movements of the wax as it cools and solidifies can then allegedly be read to forecast auguries of the future. Another method more commonly practiced in the contemporary era is studying the burning of an ordinary candle. The movements and erratic actions of the flame are then said to predict the future.
Carromancy also has roots in ancient Celtic times. According to scraps of knowledge salvaged from around the period CE 500, it appears that the candle burned during a druid's vigil was poured into a bowl and then into a clear pool of cold water. The auguries for the future could then be read.