The Morgan Library & Museum is exhibiting the unleashed imagination of Jean-Jacques Lequeu, who reveled in light and pleasure.

Nearly 60 of his voluptuous, perfectionist pen-and-wash drawings (out of some 800) have traveled from the National Library of France for “Jean-Jacques Lequeu: Visionary Architect,” a bewitching exhibition at the Morgan Library & Museum. (The show follows a larger show at the Petit Palais in Paris; another version was seen last year at the Menil Drawing Institute in Houston.) These painstaking sheets, capricious or perverse, steeped in powder blue and misty rose, are a remarkable achievement of the later Enlightenment — and yet they have much more to offer young architects today than a drawing lesson. When the building contracts dry up, you realize your one true client is desire.

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