People who write notes in ink must be very sure of their thoughts. I write notes in pencil: It seems more polite. Penciled notes are always provisional and erasable. But the apparent humility—or, perhaps, smug performance of humility—in my choice of penciling is counterbalanced by the fact that I eschew the humble wooden pencil. I must have a mechanical pencil, the kind you click to advance the lead. And when I say “a mechanical pencil,” you should know that I mean “lots of mechanical pencils.”

Cheap, plastic mechanical pencils; expensive polycarbonate mechanical pencils; tiny, slim aluminum mechanical pencils; and finely-engineered mechanical drafting pencils: I have them all. I use them to write in my notebooks, in the margins of printed books, and on manuscript paper for musical composition. I am an incorrigible mechanical penciler. I will never have enough mechanical pencils.

A good mechanical pencil is a beautifully-made object. Architects have long sworn by the original German model of my prized Rotring 600, now manufactured in Japan: Its all-metal barrel is hexagonal, so that it doesn’t roll down the drawing-board, and it is an instrument of exquisite heft and balance. (The tactile positivity of its lead-advance button mechanism is a perpetual delight. This pencil is, quite literally, clickbait.) But a mechanical pencil is also, simply, more practical. The existence of pencil sharpeners or pencils shrunk to tiny stumps through long use are just foolish rumors of a bygone age. The ordinary, dumb wooden pencil is, in the poetic words of Henry Petroski—author of The Pencil: A History (1989)—“designed to be destroyed.” A mechanical pencil doesn’t require sharpening and is always the same length, so that its weight and handfeel remain constant. It is obviously an improvement, a superior piece of gear.

When you look into the matter, though, you discover a curious fact: The first known illustration of any pencil depicts something that resembles a mechanical pencil as much as it does the wood-cased kind, in which the lead is permanently bonded to the wood that encloses it. In 1565, the naturalist Konrad Gesner published a book about fossils that featured a drawing of a new kind of writing implement for taking notes in the field, apparently of the author’s own invention. “The stylus shown below,” the accompanying text explains, “is made for writing, from a sort of lead (which I have heard some call English antimony), shaved to a point and inserted in a wooden handle.” So the “lead” (actually graphite) is separable from the handle. But there is no clever mechanism to advance the lead, as one finds in a modern mechanical pencil, so it remains a primitive device.

While the wood-cased pencil soon became commonplace, more sophisticated versions of a rigid sleeve in which the lead could move independently took longer to appear. In one 1636 example, a brass holder used a spring to push out the lead. Henry Petroski thinks this may deserve the title of “the first propelling pencil.” But mechanical pencils really took off only in the 19th century. An English engineer named Sampson Mordan patented his “ever-pointed” pencil in 1822, and the American watchmaker James Bogardus patented his own “forever pointed” pencil in 1833. By the late Victorian era there was a craze for “magic” pencils in brass or gold, disguised as lucky charms and sometimes sold along with matching toothpicks and ear spoons. Such pencils, though, had thick leads, and slack machining tolerances meant that there was a disturbing amount of play in their tips. They were not yet reliable tools for serious writing or drawing.

We still await an ear-spoon revival, but the mechanical pencil enjoyed a second, and permanent, revolution in 1915. In Japan, Tokuji Hayakawa produced a nickel-bodied device, the “Hayakawa Mechanical Pencil," with an internal lead-propelling mechanism of brass and a rifled shaft. Later iterations were christened the “Ever-Ready Sharp Pencil” and then simply the “Ever-Sharp Pencil.” It was such a success that Hayakawa eventually renamed his corporation Sharp—the same company that today is known mainly for its electronics. Similar improvements were made by the American Eversharp pencil, introduced in 1916. Within five years, 12 million Eversharps had been distributed throughout the U.S. The mechanical pencil was promoted as a cost-saving and efficiency-improving measure for office work, since no time was wasted in sharpening it. With advances made by manufacturers in Germany and Japan, it was later enthusiastically adopted by engineers and architects, especially once very fine lead (the now-familiar 0.5-millimeter diameter) became available in specialist drafting pencils in 1961. By the 1970s, more than 60 million mechanical pencils were sold worldwide every year.

In an early example of how office work can be made to sound more exciting by likening it to military adventure, one early-20th-century advertisement boasted: “Eversharp leads are smooth, strong, and fit Eversharp like ammunition fits a gun.” Yet even a premium metal-jacketed mechanical pencil, for all its military-tool bravado, has a crucial weakness. For the mechanical pencil is an exoskeletal organism. Its epidermis provides the structural rigidity within which the vital organ, the lead, is protected. And yet at the same time this thin spindle of graphite must protrude from the body to enable the user to make a mark with it, creating a point of extreme vulnerability.