"I've stopped for a few days in Aix," Claude Mellan wrote to the print dealer François Langlois in the summer of 1636, "at the house of Monsr. du Peiresc, whose portrait I've made and am sending you." A Provençal attorney, collector, and polymath whose areas of expertise included archaeology, astronomy, botany, geology, geography, mathematics, numismatics, and zoology, Nicolas-Claude Fabri de Peiresc (1580-1637) had met Mellan in Paris in the early 1620s and paid the young artist's way to Rome, encouraging him to deepen his acquaintance with antiquities in hopes that Mellan would return to France and help publish Peiresc's own collection. This portrait dates to Mellan's 1636-1637 return journey from Rome to Paris, when he stopped in Aix-en-Provence to visit his longtime friend and benefactor just months before Peiresc's death. Physically frail and careworn but fiercely—indeed, almost alarmingly—present, Peiresc looks back at us from Mellan's little sheet with all the blazing intensity of his formidable intellect. Here is an exacting portrait of a great mind. The chalk design, clearly made from life, and rediscovered just last year, served as the basis for a more formal engraved portrait of Peiresc, an early proof of which Melian may have sent to Langlois with his letter. Writing, in turn, to his fellow amateur astronomer and libertin érudit Pierre Gassendi in August 1636, Peiresc remarked, "We have M. Mellan, one of the great painters of the age, and the most precise engraver there has ever been." Mellan's chief project in Aix was to be the engraving of a lunar map sketched by Gassendi the previous year. The craggy topography of Peiresc's face and the pitted surface of the moon suggest an unexpected rhyme between these two very different projects; Mellan's muchprized precision, in any case, is the hallmark of both resulting prints. The subtlety of his line work on the copper plates, however, demanded a degree of technical sophistication in the printing apparently unavailable in Aix. Neither the lunar map nor the engraved portrait of Peiresc would be published before his return to Paris in the spring of 1637. Peiresc maintained an enormous correspondence with the likes of Galileo Galilei, Cassiano dal Pozzo, Anthony van Dyck, and Peter Paul Rubens. With the last of these, he had planned to issue an edition of antique engraved gems, and it was Rubens who put into words the difficulty of capturing Peiresc's likeness: "A great nobility radiated from his face, a spiritual something that is not easy to render in paint." Mellan, working in the humble medium of chalk, proved up to the task.