The three foot theodolite made by Cary for the Great Survey of India, 1802.

UNITED KINGDOM - MARCH 17: The 3 foot theodolite made by Cary ,and revised by Barrow, photographed on the gallery during the exhibition 'Science in India' at the Science Museum, London in 1982. Weighing over 1000 pounds, the theodolite was taken to India by Captain Lambton in 1802 and later used by Colonel Sir George Everest (1790-1866), Surveyor General of India, in the Great Trigonometrical Survey of India (1830-1843). The equipment's extreme solidity was needed to ensure that the readings were of the highest accuracy. In 1849, survey officer James Nicolson also used this theodolite to establish that a peak on Mount Everest, then known as peak 'b', was the highest in the world. In 1865, the mountain was named after George Everest by the Royal Geographical Society as a tribute to his pioneering work in mapping India. This tribute came in spite of Everest's own belief that mountains should be known by their local names.

(Photo by SSPL/Getty Images)