Reading the residue in a cup requires a drink that leaves one, and the history follows the drink. Coffee reached the Ottoman world before tea reached Europe, and reading the grounds is attested there earlier; the practice remains common across Turkey and the eastern Mediterranean, with its own conventions about turning the cup and letting it cool. Tea leaf reading in Britain and Ireland becomes visible from the eighteenth century, after tea itself becomes affordable, and it flourished as a domestic and largely female practice.
Its literature is a nineteenth and twentieth century phenomenon. Cheap printed manuals set out alphabetical dictionaries of symbols, an anchor for security, a snake for an enemy, a ring for a marriage, and it is these books rather than any older tradition that fixed the meanings most readers now expect. They were sold alongside dream dictionaries and fortune-telling card manuals to the same audience.
The mechanism is not contested by anyone, including many practitioners. A random distribution of dark particles on a pale surface gives the visual system exactly the conditions in which it produces recognisable forms, and different readers see different things in the same cup. The strength of the practice lies in what happens next: the reader speaks, the sitter responds, and the reading is built between them.
It is the most domestic of the divinatory arts in this atlas, requiring no equipment beyond the cup already in hand.