The operator first muttered over the crystal (a beryl was preferred) certain formulas of prayer, and then gave it into the hands of a young man or a virgin, who thereupon, by oral communication from spirits in the crystal, or by written characters seen in it, was supposed to receive the information desired. [Century Dictionary]
"divination by smoke," c. 1600, with -mancy "divination by means of" + Latinized form of Greek kapnos "smoke," which is of uncertain origin, perhaps a non-Indo-European substrate word that also produced Lithuanian kvapas "breath, smell," kvepiu, kvėpti "to gasp, breathe," Latvian kvept "to smoke, smell," and perhaps Latin vapor.
There were various methods of practicing rhapsodomancy—Sometimes they wrote several verses or sentences of a poet, on so many pieces of wood, paper, or the like; shook them together in an urn; and drew out one, which was accounted the lot. Sometimes they cast dice on a table, whereon verses were wrote; and that whereon the dye lodged, contained the prediction. [Chambers' "Cyclopædia," London, 1738]
1640s, "dowsing, use of a divining rod" (especially to find things hidden in the earth, ores or underground water), with -mancy "divination by means of" (from Greek manteia "divination, oracle") + Greek rhabdos "rod, wand; magic wand; fishing rod; spear-shaft; a staff of office; a rod for chastisement; twig, stick." Greek rhabdos is from PIE *wer- (2), base of roots meaning "to turn, bend" (source also of Lithuanian virbas "twig, branch, scion, rod," Latin verbena "leaves and branches of laurel").
The Greek noun was used to represent Roman fasces. Related: Rhabdomantic; rhabdomancer.