The Cosmographia of Petrus Apianus was one of the most popular books on cosmography ever published. One of the reasons for its enormous popularity was the book's inclusion of ingenious paper devices, called volvelles, which enabled one to solve practical mathematical problems relating to time telling, the calendar, astronomy and astrology. This amazing paper instrument was designed to show the limits of the horizon if the zenith is known; alternatively, if a known star grazes the horizon, then one can determine the point overhead. It is a beautiful example of woodblock printing with an elaborate rotating pointer and a stationary central disc. On verso are a diagram of the world's parallels and two wonderful woodblock initials; a "L" and a "P".

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