The monstrance clock, or mirror clock, developed during the Renaissance. The monstrance was a cross-shaped gold or silver vessel which played an important part in church ritual and often incorporated sacred figures as part of the design. The clock made use of a rotating ball at the top or in the base to indicate the time of day. Monstrance clocks and crucifix clocks remained fashionable until the eighteenth century.
Pop culture references include the song "Monstrance Clock" by Ghost. The song itself has themes of Satanic Ritual, rather than Renaissance-age Christianity.