time candle

plural time candles

1. uncommonA candle that burns at a uniform rate and is used to measure the passage of time.

   This particular use of the time candle, however, is problematic.

   1928, “How Hamilton Watch Uses The Historical Display”, in Advertising & Selling, volume 12, page 69

   2 more examples

   Some "knappers" still employ time-candles in lieu of clocks and watches, wherewith to reckon the working hours.

   1906, H.G. Archer, “The Oldest Industry In England”, in The Wide World Magazine, An Illustrated Monthly of True Narrative, Adventure, Travel, Customs and Sport, volume 16

   In Fadius's dingy room in Messantia, Alcina sat alone, holding her obsidian amulet before her and watching the alternate black-and-white bands of the time candle.

   1979, L. Sprague de Camp, Lin Carter, Conan the Liberator, page 108