used this device for his observation of what is known today as Halley's Comet at the turn of the 14th century. In the early 1300s, John of Murs mentions the torquetum as his defence "of the reliability of observational astronomy", thus further solidifying its practicality and viability in ancient astronomy. Additionally, Johannes Schoner built a torquetum model for his own personal use in the observation of Halley's Comet in the 1500s. The best-documented account of the torquetum was done by Peter Apian in 1532. Peter Apian was a German humanist, specializing in astronomy, mathematics, and cartography. In his book Astronomicum Caesareum (1540), Apian gives a description of the torquetum near the end of the second part. He also details how the device is used. Apian explains that the torquetum was used for astronomical observations and how the description of the instrument was used as a basis for common astronomical instruments. He also notes the manufacturing process of the instrument and the use of the torquetum for astronomical measurements. Components The torquetum is a complex medieval analog computer that measures three sets of astronomical coordinates: the horizon, equatorial, and ecliptic. One of the defining attributes of the torquetum is its ability to interconvert between these three sets of coordinate dimensions without the use of calculations, as well as to demonstrate the relationship between the same coordinate sets. However, it is a device that requires a thorough understanding of the components and how they work together to make relative positional measurements of certain celestial objects. The anatomy of the torquetum involves many different components, which can be grouped into subdivisions of the torquetum structure, those being: the base, the midframe, and the upperframe. The base starts with the tabula orizontis, which is the bottommost rectangular piece in contact with the ground, and this component represents the horizon of the Earth, relative to the point of measurement. Hinged to the tabula orizontis is a similarly shaped component, the tabula quinoctialis, which represents the latitude of the Earth. This piece can rotate up to 90 degrees, coinciding with the latitudinal lines of the Earth from the equator to the poles. This angle of rotation is created by the stylus, which is an arm mechanism that pins to the slotted holes, which are part of the tabula orizontis. The midframe of the torquetum consists of a free-spinning disk (unnamed) that can be locked into place,