591. An Important Papal Horizontal Dial, dated 1591 
Attributed to Carlo Plato, Rome. Dated MDXCI [1591].
With the engraved name and coat of arms of Pope Clement VIII.
Gilt brass. Total width 26, Height 11.5 cm.

SEK 1.500.000 – 2.000.000     € 142.000 – 189.000 

In original leather case with papal insignia.

Provenance:
Pope Clement VIII (1536-1605), according to the engraving.
Later in the collection of the noble family Leijonhufvud, Göksholm castle, Sweden.

In the Italian states during the sixteenth century, the business for scientific instrument makers flourished with products often rivalling those of the prolific centres of scientifica manufacturing in central Europe. Italian artisans and families of scientific instrument makers were either independent or, more often, in the service of princely families such as the Medicis, and emphasis laid on astronomical instruments, especially before the sixteen hundreds. Well-known examples from Tuscany include Giovanni Battista Giusti, the Della Volpaia family, and the cartographer Stefano Buonsignori who completed the Sala delle Carte Geografiche [Map Room] in the Palazzo Vecchio in Florence.

Roman commissioning culture was at the time more centered around ecclesiastic power, and high-level instrument makers were most often connected to the Pope or the grand families with papal interests. It was in this milieu Carlo Plato worked. Biographical data on him are scarce, but from his few signed instruments we learn that he was active in Rome during the last decades of the 16th century. He made elaborate and very ornate astronomical and time-measuring instruments, such as armillary spheres and sundials.

Description
The instrument is composed of a disc engraved with different sets of dials, suspended in a two-tiered octagonal stand. The disc can swivel between its two horizontal positions to expose different sets of dials to the sun, and further holds a gimballed compass to assist in orienting the instrument. The disc is locked in place via a hasp on the underside of the stand’s top tier.

Side A – Most notable on this side is the  papal coat of arms with the escutcheon of Pope Clement VIII, juxtaposed by a text scroll flanking the pivoted compass that reads ”CLEMENS VIII *P*O*MAX” (most likely for ”Pontifex Optimus Maximus”, although ”Optimus” was rarely used in regard of popes). The coat of arms is flanked by the text ”Elevatio Poli XLII Gradvv”, and in the centre is the main dial graded 10–23 with continuous lines divided by punctuated lines. The gnomon is placed somewhat off-centre, and the disc’s edge is circumscribed with a 360 degree scale, subdivided by singular degrees.

Side B – This side provides three independant dials, each with its own gnomon. Opposite the compass are the Astronomical hours scale (Horæ Astronomice),
numbered I to XII to VII. To the left of the centre is the Planetary hours scale (Horæ Planetariæ Sive Canonicæ), numbered 1–11, and to the right, the Babylonian hours (Horæ Babilonicæ Sive Ab Ortv), numbered 1‑14. The edge is further inscribed with ”Ad Polvm XLII Gradvvm” and a text scroll that reads ”ROMÆ ANNO DOMINI *M*D*XCI”.

Compass – The compass housing is circular and covered with glass. It is inscribed with the initials of the names of the winds and the domed bottom of the compass is weighted so that it remains horizontal when turning the dial.

Stand – The stand is a two-tiered octagonal structure, joined by eight Doric pillars standing on eight semi-spherical feet. The bottom tier is decorated with engraved flowers and paired cornucopias, while the top-tier is engraved with a calendar and zodiacal signs, along with the names of the twelve classical winds and cardinal points on the limb:
SEPTENTRIO Tramontana [N]
Boreas Greco [NE]
ORIENS Levante [E]
Eurus Scirocco [SE]
MERIDIES Ostro [S]
Africus Leberio [SW]
OCCIDENS Ponente [W]
Circius Maestro [NW]

They follow closely the naming standard propound by the Portuguese cartographer Diogo Homem (1521‑1576) in his Atlases.

Case – The octagonal wooden lidded case is covered in red leather incised with lines and gold leaf patterns. The inside is partly clad with dark chamois leather, and the hinge, lock and feet are made out of bronze. The lid has a heavily worn central papal coat of arms on a red painted background.

Attribution
The attribution to Carlo Plato (who also signed himself as Carolus Plato or Platel) is based on the very typical design of the horizontal dial, similar to several other instruments signed or attributed to Plato’s hand. The gimballed compass is notably typical of his work, albeit none of his known sundials are mounted in a stand, nor are of this grandeur or size. For comparisons, see British Museum, reg.no. MLA 1888, 12‑1.292 and 1922,1017.1., the Oxford MHS, new inv. nos. 49535 and 46744, and Istituto e Museo di Storia della Scienza, Florence, dated 1578, inv. 246. Also see H. Higton, Sundials at Greenwich, Oxford 2002, no. 299, pp. 311‑14, and F. A. B. Ward, A Catalogue of European Scientific Instruments in the Department of Medieval and Later Antiquities of the British Museum, London 1981, no.13, p. 22.

Discussion
The general adaption of the dials to the forty-second latitude, which passes just north of Rome, confirms its origin in the city, and the inscription on side B dates the instrument to 1591. Unfortunately, it predates the reign of Pope Clement VIII with more than a month, as he held the pontificate from 2 February 1592 until his death in 1605. But the years around 1591 were turbulent for the Holy See with several popes passing in rapid succession. After the death of Pope Sixtus V in 1590, the conclave elected Giovanni Battista Castagna, who is perhaps most remembered for a notable short reign of only thirteen days as Pope Urban VII (15–27 September 1590). He was in turn succeeded by Pope Gregory XIV reigning for ten months (5 December 1590 –16 October 1591) and shortly thereafter followed by Pope Innocent IX, reigning for only two months (29 October – 30 December 1591). Following this papal surge in the early 1590s, the Florentine Ippolito Aldobrandini as Pope Clement VIII had a long and rather successful papacy until his death thirteen years later.

In addition to the date 1591 on the instrument, predating the reign of its dedicatee Pope Clement VIII, we find some manipulations of the name scroll and papal escutcheon. The heraldic achievement with the crossed keys and papal tiara is completely original (just as the dating), but the oval escutcheon in the centre seems altered along with the papal name scroll at the bottom. With the previously disruptive period in mind, a feasible hypothesis is that the instrument was commissioned for one of Pope Clement VIII’s predecessors but never delivered. Keen on adapting the instrument to the new Pope, the instrument maker polished away the previous name and escutcheon and replaced them with those of Clement VIII. A similar alteration is found on a pocket compendium dated 1582/83 and attributed to Plato (now in the Royal Museum in Greenwich, inv. AST0136), in which a complete dial has been engraved on top of a previous one that had been scraped away, i.e. the practice was not unseen of.

In conclusion, this is a remarkable Italian scientific instrument from the late sixteenth century of a magnitude that rarely surfaces the art market.

Greger Sundin, Uppsala

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