An hourglass is a wasp-waisted glass container, partially filled with sand; it was used for measuring time, by letting the sand trickle from the top half to the bottom. The first known illustration of an hourglass is a fresco in the Palazzo Pubblico in Siena, c.1339 [Eric Bruton, The History of Clocks and Watches, p.27]; it’s found in the arms of White, 1534 [Parker 335] and of von Kerstlingerode, 1605 [Siebmacher 179]. The hourglass is palewise by default.
The hourglass should not be drawn as transparent glass, through the use of chasing or voiding; it should be solidly tinctured.
Galleron de Cressy bears: Azure, three hourglasses Or.
Gareth de Grey bears: Sable, an hourglass argent.
Caoimhín o Fiodhabhra bears: Per chevron azure and Or, three hourglasses counterchanged.