Lodestone

The Lodestones were a type of time travel technology used by the Osirian civilisation.

They took the form of an Egyptian sarcophagus and were entrances into a time space tunnel. When activated, the coffin shaped device loses its stone form and becomes a visible doorway with energy spiralling in its form.

One such lodestone threw the Doctor's TARDIS off course and allowed Marcus Scarman to travel to 1980 in order to destroy Sutekh's prison thus freeing his master. (DW: Pyramids of Mars)

Lodestones differed from most forms of time travel in that there was a 1:1 ratio between the distance in time traveled and the time experienced for the traveler; for example, a person on a journey 70 years back in time through a lodestone would age 70 years. As the Osirans lived thousands of years, this was not a concern to them. (MA: The Sands of Time)