Jan Bruegel the Elder’s “Windmill” (1605–15), a small, unassuming drawing in pen and brown ink with touches of brown wash and traces of graphite, is as taut as a wind-up toy, as ready as a loaded catapult, and — with its paddles trailing, undulating, and windwhipped — as light and graceful as a kite’s tail. Elevated above the ground and teetering on a pyramidal base made up of wooden beams, the windmill is treated more as a ship or as a portrait bust than as an architectural study.

The drawing, a poetic exploration of the dynamics of — and the precariousness of our attempts to control — nature, is one of the many masterpieces in “Private Treasures: Four Centuries of European Master Drawings,” which opens today at the Morgan Library & Museum.

The opening of the Morgan’s show coincides with, and dutifully anchors, the weeklong exhibit “Master Drawings in New York 2007,” a joint exhibition between 16 galleries, including Sotheby’s, Christie’s, Richard L. Feigen & Co., Kate Ganz USA Ltd., and Margo Gordon, among others, most of which are within walking distance of one another on the Upper East Side. A veritable feast for art lovers and collectors, “Master Drawings” offers more than 1,000 works from the Renaissance through the 20th century by artists such as Antoine Watteau, Annibale Carracci, Jean-Honoré Fragonard, Julio González, and Pablo Picasso. “Master Drawings” will give you a sense of what is currently available for purchase, and it will also act as a barometer against which you can judge “Private Treasures,” a private collection amassed during the last 11 years.

“Private Treasures,” comprising some 93 works on paper from an anonymous collection of roughly 110 drawings, many of which have not been exhibited publicly, is organized by Rhonda Eitel-Porter and Jennifer Tonkovich at the Morgan, and Margaret Morgan Grasselli and Andrew Robison at the National Gallery in Washington, D.C., where it will travel from New York. Arranged chronologically, the exhibit spans the early 16th through the early 20th centuries. Accompanied by a wonderful catalog, the show includes works by Italian, French, Netherlandish, British, and German artists, and amounts to one of those glorious exhibitions that — no offense to its organizers — basically curates itself.

The exhibition’s strengths (of which there are many) and its weaknesses (of which there are a few) therefore rest with the collector. To be sure, “Private Treasures,” though the owner of its works remains anonymous, is a vanity show that will provide him or her with a coffee table book and plenty of bragging rights; but it is also worth remembering that private collectors are often at the heart of our museums’ collections. New York’s Frick Collection and Morgan Library & Museum reflect the taste of private collectors. In part, so does the Metropolitan Museum of Art, to which many collectors have donated works, including J. Pierpont Morgan, who donated more than 7,000 objects from his collection, chiefly medieval and ancient works .

If not always a collection of greatest hits, “Private Treasures” reflects a well-heeled catholic taste and brings us enough “A” sides by A-list artists — Anglo Bronzino, Watteau, Fragonard, Francesco Guardi, Odilon Redon, John Constable, Théodore Rousseau, Jean-Auguste-Dominique Ingres, Eugène Delacroix, the Tiepolos, Gian Lorenzo Bernini, and Claude Lorrain — to make up for its “B” sides and B-list artists — so-so works by Käthe Kollwitz, Edgar Degas, and Federico Barocci, among others.

Among the numerous gems are drawings by Fra Bartolommeo, whose study “The Virgin and Child Surrounded by Saints and Angels” (c. 1500) is delicate and crystalline, and whose “A Fortified Hill Town” (1500–10) has an energy and brevity that foretell the landscape drawings of Cézanne. Also of interest are works by Giorgio Vasari (1511–74), who was not only the first bona fide art historian but also a painter and architect of merit. Here are studies for paintings, including one on which is written, on its verso in Vasari’s hand, a list of names and dates of artists related to the 1550 edition of Vasari’s Lives. Bernini’s “Portrait of an Elderly Man With Mustache and Small Pointed Beard” (c. 1630s or 1640s), with its frontal eyes and mouth and three-quarter head and nose, rocks from side to side, and then engages, locking our eyes with a steadfast directness. Claude’s “Landscape at Sunset With Mercury and Battus” (c. 1663), a study for a painting, represents, as does the show’s landscape drawings by Fragonard, both artists at the top of their games. So does Watteau’s troischalk drawing “A Man Playing the Guitar” (c.1717–18). The drawing is free and loose; the musician’s hand is solid and sculptural; and the whole drawing vibrates as if he were made of guitar strings.

One of the show’s standouts is Sinibaldo Scorza’s pen-and-ink drawing “Orpheus and the Animals” (1620–21), a strange peaceable kingdom in which Orpheus, playing the violin, holds court at the composition’s center. “Orpheus” is certainly not one of the strongest works in the collection — spatially confused, much of the drawing’s fairytale flora and fauna hover around the musician like weightless bubbles. But its inclusion, unlike that of many of the exhibit’s stars, demonstrates a peculiarly personal taste — perhaps a love of Orpheus or of animals and trees, all of whom dance or sway or are rapt by the poet’s song. Or maybe the drawing uncovers romanticism in its owner. Either way, it was while looking at this drawing that I felt as if I were encountering not a collection of drawings but, rather, the heart of a collector.

The Morgan Library & Museum until April 8 (225 Madison Ave., between 36th and 37th streets, 212-685-0008);

“Master Drawings in New York 2007” at various venues tomorrow until January 27 (212-755-8500, masterdrawingsinnewyork.com).