Religious texts of the period make many more references to the irreversible passage of time, and artistic themes appeared at this time such as "Vanitas", a reminder of death in the form of a still life, which always included a watch, clock, or some other timepiece. The relentless ticking of a clock or watch, and the slow but certain movement of its hands, functioned as a visible and audible "memento mori". Clocks and sundials would be decorated with mottos such as "ultima forsan" ("perhaps the last" ) or "vulnerant omnes, ultima necat" ("they all wound, and the last kills"). Even today, clocks often carry the motto "tempus fugit", "time flies." Mary, Queen of Scots was said to have owned a large watch made in the shape of a silver skull.