Onimancy (or Onycomancy) is a form of divination based on the observation of the angel Uriel. It can also refer to the interpretation of spots on human nails.
Derived from the Greek onux ('nail') and manteia ('prophecy')
Oil of olives or walnut oil mixed with tallow is placed on nails of the right hand or in the palm of an unpolluted boy or a young virgin girl. To seek after money or hidden objects, the child must face the east direction; to know about romance and crime, the child must face the south; and for robbery inquiries, the child must face the west.
After that, the child must repeat the 72 verses of the Psalms, which the Hebrew Kabbalists collected for Urim and Thummim. These are found in the third book of Johann Rechlin on Kabbalistical art (De arte cabalistica, 1517), and the treatise De verbo mirifoco (c. 1480). In each of these verses, you can find the venerable name of four letters, and the three lettered name of the seventy-two angels, which are referred to as the sacred name Shemhanphorash and was hidden in the folds of the tippet of the high priest.
When the child or student had completely repeated all the verses he was told he would “see wonders.”
In its second form, Onimancy is similar and somewhat more practical, being an interpretation of personal characteristics from the nails as a minor phase of Palmistry. Diviners in Brazil prepare the thumbnail by coating it with ash and oil to provide a reflective surface for scrying when dry. Another way of divining the future from a fingernail or toenail was to coat it with a liquid which would dry with a lace-work of fine cracks and read the design of the cracks.