Professor Cornelius Perkins was an explorer. In 1873, he and Dr Hugo Somesby were on an expedition to the Amazon rainforest, looking for the city of the Maygor tribe, the legendary Lost City of Gold. On 1 May, the thirty-sixth day of their search, they disappeared. In Perkins' final diary entry that day, he described "a frog the size of a rhinoceros" with the leg of one of the natives in its mouth.
In fact, they had entered a time bubble created by the Luron Godwin to protect his crashed spaceship. Due to the slowed passage of time inside the bubble, when his great-grandson Edward, the Fourth Doctor and Leela tried to find him 104 years later, only a month had passed for the Professor. (AUDIO: The Valley of Death)