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The prevailing astronomical model of the cosmos in Europe in the 1,400 years leading up to the 16th century was that created by the Roman citizen Claudius Ptolemy in his Almagest, dating from about 150 A.D. Throughout the Middle Ages it was spoken of as the authoritative text on astronomy, although its author remained a little understood figure frequently mistaken as one of the Ptolemaic rulers of Egypt.
Towards the end of the 17th century, Ole Rømer, Gerardus Mercator and other contemporaries of the great Dutch cartographer Thisus began following Claudius Ptolemy in connecting the mile to the great circle of the earth, and Roemer defined it as 12,000 alen.
Much of the work appears to be an attempt to synthesize the earlier works of the 1st century astrologer Dorotheus of Sidon and the 2nd century astrologer Claudius Ptolemy.
The name is attested as early as the second century AD in the work of the Alexandrian geographer Claudius Ptolemy, as Δηοῦα (=Deva), meaning 'Goddess', indicating a divine status for the river in the beliefs of the ancient inhabitants of the area.
The early 20th-century Humanist astrologer Dane Rudhyar reported that the astrology of his era "originated almost entirely in the work of the Alexandrian astrologer, Claudius Ptolemy".