Albus Dumbledore kept a variety of silver instruments in his office at Hogwarts School of Witchcraft and Wizardry. They made constant whirring noises and occasionally emitted puffs of smoke. These instruments include a rotating tower and magnification devices. In December of 1995, by making careful observations of the snake-shaped smoke emitted from one of the devices, Dumbledore gained greater insight regarding Nagini's nature as a Horcrux, as well as Harry Potter's mental connection to Voldemort.