On the heels of “John Singer Sargent: Portraits in Charcoal,” the Morgan Library & Museum has mounted “Jean-Jacques Lequeu: Visionary Architect; Drawings from the Bibliothèque Nationale de France,” on through May 10. Count both shows as displays of utter virtuosity, by artists whose control of their respective media is truly something to behold. What charcoal was for Sargent, ink was for Lequeu: an extension of vision so unfettered and supple as to be preternatural. The richness brought to Lequeu’s drawings—the surfaces of which are simultaneously malleable as velvet and impermeable as pewter—are rendered more astonishing by the meticulousness of his line and the scale at which it is employed. He was an exacting miniaturist. Visitors are urged to use a set of magnifying glasses installed at the entrance to the show. Rare is the artist whose skills reward such close inspection. Lequeu, like Sargent, is one of them. And that is where any and all correspondence between the two artists comes to a halt.

Jennifer Tonkovich, the Morgan’s Eugene and Clare Thaw Curator of Drawings and Prints, could have titled the exhibition “And Now for Something Completely Different,” and it wouldn’t have come close to describing how distinct Lequeu’s works on paper are from those of Sargent. Social bonhomie has fled the galleries; Lequeu’s art is private to a fault. Many of the differences can be chalked up to context and chronology, but the main dissimilarity stems from the narrowness of the Frenchman’s aesthetic. An outsider artist before the term was coined, Lequeu was at the mercy of peculiar and often unseemly fascinations. It is, of course, these fascinations that make him a figure worthy of note. Oddballs are diverting, and when they’re as skilled as this one they merit consideration. Still and all, the amount of pleasure derived from “Visionary Architect” will depend on whether one thinks of art primarily as a means to elaborate our experience of the world or as a forum for one man’s idiosyncrasies.

Jean-Jacques Lequeu, The Great Yawner, 1777–1824, Pen and black ink, brown and gray wash, red chalk, Bibliothèque nationale de France

Born in Rouen to a family of carpenters, Lequeu (1757–1826) exhibited talent and initiative early on. He attended the Royal Academy of Architecture in Paris and found work with Jacques-Germain Soufflot, the neo-classical architect responsible for the Pantheon, a former church located in the city’s Latin Quarter. Lequeu had an iffy career as a practicing architect. His professional ambitions—which, if his design for the Hôtel de Montholon is an indication, were grandiose and finicky—were waylaid by Soufflot’s death in 1780 and no less by the Revolution. Lequeu supported the new regime, but his enthusiasm did nothing to gain him notice or favor. Employed as a civil servant, he muddled by as a surveyor and cartographer. Draftsman’s Tools (1782), a drawing that serves as an inventory of the trade complete with marginalia, was part of an unrealized textbook titled Civil Architecture. Most everything Lequeu put his hand to fizzled. His architectural plans became increasingly implausible. Walls decorated with milk and sugar, a building shaped like a cow, and a chicken coop with a minaret—sure, why not?

The “visionary” gambit of the exhibition title should be taken at face value. Though the Morgan does attempt to sell Lequeu as a harbinger of architectural possibility, the appeal of his art is, in fact, its impossibility. It speaks to the power of Lequeu’s imagination that studies for a “Temple of Equality” or an “Indian Pagoda of Intelligence” retain a quasi-futuristic edge some two hundred years after the fact. A few observers have suggested that Lequeu was some kind of proto-postmodernist, and they’re not far off the mark. There is an inherent perversity in how Lequeu mixes but doesn’t quite match stylistic tropes, incongruent ornamentation, and cross-cultural references. His lovingly delineated bizarreries are, however, absent of irony. His ickiness and isolation aren’t mere caprice; they have too much integrity. A series of self-portraits seen at the front end of “Visionary Architect” are, for all their self-consciousness and wit, indicative of a temperament that just can’t help itself. The mannered neurasthenia of The Great Yawner (1777–1824) is particularly creepy. All is not well in Lequeu Land.

Jean-Jacques Lequeu, Indian Pagoda of Intelligence, from Civil Architecture, n.d., Pen and black ink, brown wash, watercolor, Bibliothèque nationale de France

Lequeu died destitute, alone, and forgotten. He had the wherewithal to consider posterity, donating the entirety of his output—some eight hundred drawings—to the French state. The obscurity to which Lequeu was subsequently consigned can be attributed, in no small part, to his own doing. Numerous drawings dedicated to sexual preoccupations of a rather peculiar sort don’t readily lend themselves to public display, let alone public acclamation. A small selection is on view, the gentlefolk at the Morgan having spared us Lequeu’s more clinical forays into gynecology and tumescence. (Photos of these can be seen in the catalogue.) Lequeu’s brand of eroticism is guileless and, as such, unnerving. A nun exposes her breasts in a deadpan manner; a bacchante plays a flute from her backside; a Michelangelo-esque nude, radically foreshortened, attempts to capture a bird while tumbling within an architectural niche—each of them is rendered with a tensely coiled attention to volume and detail. Here is desire without humanity: an array of obsessions that transforms pleasure into something brittle and, it almost goes without saying, unattainable. A little of Lequeu goes a long way. You won’t necessarily be happy to make his acquaintance, but neither will you forget this visionary architect.