Petrus Apianus' illustrated book, "Astronomicum Caesareum" (1540) is depicted and described. The Sackner Archive holds a facsimile edition of this work. The catalogue entry of this original masterpiece states: "This copy is a magnificent example of 16th-century bookmaking. The Astronomicum Caesareum contains a broad analysis of Ptolemaic astronomy and is notable for Apianus's pioneering observations on comets, particularly his discovery that comets always point their tails away from the sun. The elaborate folio includes more than 100 woodcut and typographic diagrams, vignettes and illustrations in the text, many with movable type." -- Source of annotation: Marvin or Ruth Sackner.