Magnus Greel's time cabinet

The time cabinet was an early experimental time machine from the 51st century which used zygma beams.

Origins
The time cabinet was developed by the Supreme Alliance. It was an unsuccessful device, as it had been based on Sa Yy Findecker's discovery of the double nexus particle, which, according to the Fourth Doctor, would lead mankind into a scientific cul-de-sac. It used the principle of a zygma beam, which if overstretched could cause a huge and catastrophic implosion. Its use could lead to severe and life-threatening mutations. It could be locked by fused molecules, and thereafter only opened by a "time key" in the form of its trionic lattice, a unique element which was central to its operation. (TV: The Talons of Weng-Chiang) Another Supreme Alliance war criminal would, however, discover means to reverse the degenerative process. (COMIC: The Time Machination)

Use of the time cabinet
Magnus Greel, the one-time Minister of Justice of the Supreme Alliance, used the experimental device when he was fleeing persecution — or prosecution — as a war criminal. This made him, as far as he knew, the first human to travel through time.

Greel arrived in 19th century China. He had to hide from Imperial soldiers for a long while, and his time cabinet was taken. George Litefoot's family got the cabinet as a parting gift from Emperor Tongzhi when they left China in 1873. They thought it was a puzzle box. He never opened it. Greel searched for the cabinet for many years. His search led him to London, where Litefoot had settled after leaving China. Greel recovered the cabinet in 1889. He committed several murders mostly to harvest the life force of innocents to keep himself together, though this actually accelerated the process of cellular degeneration which had begun when he first used the cabinet. He was killed by this degeneration when the cabinet could no longer function correctly. The Fourth Doctor destroyed the time key, rendering the time cabinet useless. (TV: The Talons of Weng-Chiang)

Behind the scenes

 * Dialogue in The Talons of Weng-Chiang indicates that the soldiers taking the cabinet served Emperor Tongzhi, whose reign began in 1861. This could be deduced as an earliest possible arrival date for Greel.