The Hourglass of Time, or just The Hourglass, is an Artifact that is present on the Prince of Persia series. It contains the Sands of Time, which are released by the Prince after the Sultan queried it glowed, and the Vizier replied that only the Dagger of Time could unlock the "marvels" inside.
On Warrior Within, the Hourglass makes an appearance in the throne room in the Fortress of Time. There, or then, the sands inside it are not the same as the Prince released in the previous installment. This time, the sands contained within the Hourglass are actually in a countdown for the creation of the Sands of Time.