The Nuttall Encyclopedia
The soothsayer who accompanied Agamemnon to the siege of Troy; enjoined the sacrifice of Iphigenia to propitiate the gods, foretold the length or the war, and advised the construction of the wooden horses, a device by means of which Troy was surprised and taken.
Wood, James, ed. Entry for 'Calchas'. The Nuttall Encyclopedia. https://www.studylight.org/encyclopedias/eng/nut/c/calchas.html. Frederick Warne & Co Ltd. London. 1900.