Pro Crisibus Morborum et Aspectibus Planetarum, Johann Zahn, Nuremberg 1696

Description
This exceptional seventeenth-century engraving is from Johann Zahn’s Specula physico mathematico historica notabilium ac mirabilium sciendorum in qua mundi mirabilis oeconomia, published in Nuremberg in 1696 by Johann Christoph Lochner. Zahn’s monumental encyclopaedia is one of the most ambitious scientific works of the Baroque period, uniting astronomy, mathematics, meteorology, optics, medicine, natural philosophy, and cosmographical speculation into a single visual system.

This plate presents the intricate relationship between planetary movements, zodiacal divisions, critical days, and the progression of illness. Physicians of the seventeenth century still relied on astronomical cycles to anticipate the turning points of disease, and diagrams such as this served as practical diagnostic instruments. The central disc arranges the zodiac around a structured sequence of geometric aspects, including oppositions, trines, squares, sextiles, and the intervals between critical days. Surrounding rings provide calibrated time divisions and planetary cycles. The flanking columns list detailed tables of planetary motion, enabling the user to cross-reference celestial activity with medical reasoning.

For collectors of early scientific illustration, the engraving represents a pivotal moment in the shift from medieval astrological medicine to observational science. Zahn’s work captures this transition with clarity and precision, documenting a world in which astronomy, mathematics, and medicine were still interdependent disciplines. For collectors of medical history, the plate is of particular interest as an authentic record of how early physicians understood crisis points, humoral shifts, and the influence of celestial forces on the human body.

Specula draws on multiple authorities: the celestial plates follow Hevelius, lunar and solar studies draw on the observations of Georg Christoph Eimmart, and several cosmographic elements reflect the influence of Athanasius Kircher. Zahn incorporated not only rigorous science but also broader natural-philosophical concerns, including imaginative theories about hidden forces in nature.

Johann Zahn (1641–1707) was a German philosopher, scientist, mathematician, and cartographer. His work Oculus Artificialis made a profound contribution to the early development of camera design and pre-photographic optical theory. He was a prolific illustrator whose engravings remain highly valued for their technical sophistication and intellectual depth.

Rarity note
Plates of this complexity from the 1696 Specula are increasingly scarce in clean condition. Many copies were damaged at the fold, trimmed by binders, or darkened through heavy handling. Medical astronomical plates, such as this example, appear far less frequently than Zahn’s cosmographic or optical diagrams and attract specialised collectors. Crisp impressions with complete architectural borders, intact numerical scales, and minimal fold wear are considered rare. This sheet, with its wide margins and strong printing, stands among higher-grade surviving examples.

Condition report
Very good condition overall. A binding crease to the left of the fold where the plate did not fully take ink. Minor imperfections consistent with age.

Literature
Specula physico mathematico historica notabilium ac mirabilium sciendorum in qua mundi mirabilis oeconomia

Dimensions
Approximately 18 inches by 15 3/4 inches, fold-out plate

Artist or maker
Johann Zahn

Medium
Engraving on laid paper

Date
1696