Apian - [Post Incunable] Folium Populi - 1533

First Edition - The Talisman of Celestial Sciences: Pietro Apiano's Harmonic Invention
The Folium Populi is one of the most curious and rare works by Pietro Apiano, a renowned mathematician, astronomer, and cosmographer of the German Renaissance. Published in Ingolstadt in 1533, it describes and illustrates a particular paper instrument shaped like a poplar leaf, designed to perform astronomical, astrological, and perspective calculations. The work, enriched with spectacular woodcuts, combines mathematical precision with symbolic imagination, revealing the Renaissance tension between science and the magical art of numbers. It is not merely a technical manual but a true object of wonder, where the instrument intertwines with representations of power and heraldic and allegorical images.
Market value
The Folium Populi by Apian is of great rarity on the antiquarian market. Complete specimens, especially in good condition, now reach values ranging between 6,000 and 12,000 euros. Copies with illustrious provenance or in excellent condition can exceed these estimates, as they serve as early and unique testimonies of Renaissance scientific ingenuity.
Rare Book Hub reports the sale of a copy for CHF 8,125 (approximately €8,000) within an estimated range of CHF 8,000-12,000.
Another sale at a Swiss auction house indicated an estimate of CHF 5,000-8,000 (approximately €5,150-8,250).

Physical description and condition
Modern binding in rigid cardboard painted brown. Frontispiece with a large figurative woodcut and text in red and black. Minimal traces of oxidation. Pp. (4); 22nn; (4).
First edition, in Latin and German, of Apian's description of his recently invented sundial in the shape of a poplar leaf. This instrument can be used to calculate the hours of the day, the times of sunrise and sunset, and the so-called 'Hebrew hours,' which divide the time between sunrise and sunset into 12 parts. The splendid woodcuts were executed by Hans Brosamer (c. 1500-1554), with his monogram on the title woodcut next to the image of an engraver's knife.
The title in this copy is in an incorrect state, with 'RFCENS' and 'RFDACTUM' instead of 'RECENS' and 'REDACTUM'.
Small wormholes touching the margin, but overall a good copy with ample margins.
Text in Latin and German, frontispiece in red and black with a finely executed woodcut by Hans Brosamer depicting a diagram of the instrument alongside a European astronomer and an Ottoman astronomer, each holding an astronomical instrument; a nearly full-page woodcut of the dedicatee's coat of arms, JG di Loubenberg; a large diagram in woodcut printed twice (in the Latin and German texts); and 7 decorative initials. Fold-out plate, included in a very limited number of copies, here reproduced on antique paper.

Full title and author
Folium populi. This instrument, invented by Petro Apiano and now rediscovered, shows in the shape of a leaf the hours of the day based on the sun's rays worldwide, including hours from sunrise and sunset, and also Jewish hours. In the new instrument, which has the form and shape of a leaf, the common hours of the day are found through the sun's shine across the entire world, and from the same, using this leaf, you can easily determine the hours from the sunrise and sunset of the sun, which are the same as the Jewish hours.
Ingolstadt: Peter Apianus, no date.
Excusum Ingolstadii, October 22, 1533. - [12] pages, 1 folded plate: illustrations; folio.
Peter Apian

Context and Significance
The Folium Populi is an extraordinary work that exemplifies the Renaissance ability to transform science into visual spectacle. It is a movable sheet, articulated in geometric shapes, which allowed for calculations related to the movement of the stars and judicial astrology. The title itself evokes the shape of the poplar, a symbol of flexibility and connection between earth and sky. The work fits within the line of Renaissance scientific inventions that combined practical utility, educational value, and a magical-symbolic dimension. Due to its combination of science and imagery, the Folium Populi stands as one of the most original creations of the university typography of Ingolstadt.

The Folium populi by Peter Apian from 1533 is equipped with a movable arm, a plumb line, a pearl, and two sights. It resembles a poplar leaf with a stem. It is used to determine equal and unequal hours, as well as the hours elapsed since sunrise and sunset.
However, it no longer appears in Apian's 'Libro degli strumenti'; it has been replaced by one of the most useful dials: the Horoscope.
It stands out for its sophisticated design and unique shape. In contrast to the seemingly austere and functional dial, it appears more like a work of art.

The dedication page of the small bilingual booklet 'Folium Populi' to the 'Nobilisimo Dño IO. GVLIELMO a Loubemberg', whose coat of arms depicts three poplar leaves, is repeated in Apian's most important preliminary work, the 'Instrument Book'.

Biography of the Author
Peter Apian (1495-1552), Latinized as Apianus, was a German mathematician, astronomer, and cartographer. Born in Leisnig, he studied in Leipzig and Vienna, publishing important works on cosmography, cartography, and scientific instruments. Among his major works are Cosmographicus liber (1524), translated into many languages, and Astronomicum Caesareum (1540), a masterpiece of Renaissance science. A professor at Ingolstadt, he received support from Charles V. The Folium Populi represents an experimental phase of his inventive genius.

In 1526, Peter Apian founded his printing house in Ingolstadt. From 1527 onwards, he taught at the university and called himself 'PETRVS APIANVS de Leysnick Mathematicus Ingolstadianus.'
In 1532, the book on the dial, 'Quadrans Apiani,' was published, followed in 1533 by 'Folium Populi,' 'Horoscopion,' and 'Instrument Book.'

This latter was a summary and partial integration of all the previous publications published on his measuring instruments. It was written in German and therefore aimed at an educated audience, but not university-level.

Printing history and circulation
Printed in Ingolstadt in 1533, the Folium Populi had a limited edition and was intended for a restricted audience of scholars, mathematicians, and princely courts. Due to its technical nature and the complexity of its illustrations, its circulation was very limited. Today, very few copies are known in public libraries; its appearance on the antiquarian market is extremely rare and always highly notable.

BIBLIOGRAPHY AND REFERENCES
Zinner, Astronomical Instruments of the 16th Century, Leipzig, 1957
Adams, Catalogue of Books Printed on the Continent of Europe, 1501–1600 in Cambridge Libraries
Houzeau-Lancaster, General Bibliography of Astronomy
VD16 A 3092
OCLC/WorldCat, record Folium Populi, Ingolstadt 1533