When it hit shelves in the 1970s, the Predictor pregnancy test, made by Organon Pharmaceuticals, went for $10. On Tuesday, the auction house Bonham’s sold the original prototype, along with the first consumer version of the test, for $11,875.

The Predictor was the brainchild of a freelance designer named Margaret Crane, who had been hired in Organon in 1967 to work on a new cosmetics line. While touring the company’s lab, she wrote in a note accompanying the Bonham’s sale,

I noticed multiple lines of test tubes suspended over a mirrored surface. I was told that they were pregnancy tests ... Each test tube contained reagents which when combined with a pregnant women's urine, would display a red ring at the base of the test tube, as reflected in the mirror.

Inspired, she set to work developing a simplified version of the test: At her home in New York, she assembled a plastic paper-clip holder, a mirror, a test tube, and a dropper, and presented her kit to Organon a few months later. In 1969, the company applied for a patent in her name.

“I thought how simple that was,” she recalled of seeing the tests for the first time, according to Bonham’s. “A woman should be able to do that herself.”

Simple, though, had been a long time in the making.

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A long, long time before women peed on sticks, they peed on plenty of other things.

One of the oldest descriptions of a pregnancy test comes from ancient Egypt, where women who suspected they were pregnant would urinate on wheat and barley seeds: If the wheat grew, they believed, it meant the woman was having a girl; the barley, a boy; if neither plant sprouted, she wasn’t pregnant at all. Avicenna, a 10th-century Persian philosopher, would pour sulfur over women’s urine, believing that the telltale sign was worms springing from the resulting mixture. In 16th-century Europe, specialists known as “piss prophets” would read urine like tea leaves, claiming to know by its appearance alone whether the woman who supplied it was pregnant.

But as strange as it sounds to modern ears, “piss prophecy,” so to speak, never really fell out of favor—at least not with pregnancy tests. The name changed, and the tools changed. And what also changed, most significantly, was who got to play the part of the prophet.

Doctors in the 18th and 19th centuries, shaped by the scientific discourse of the Enlightenment, abandoned the belief that urine could simply be eyeballed, instead pursuing the idea that it must contain some less easily identifiable traits—some bacteria or crystal structure, visible only under a microscope—that could signify a pregnancy. Around the end of the 19th century and the beginning of the 20th, scientists began to discover the chemicals that regulated various functions in the human body, including reproduction. The word “hormone” was coined in 1905; in the 1920s, human chorionic gonadotropin (hCG)—a hormone found in high concentrations in pregnant women—was identified.

The first true precursor to today’s pregnancy test was developed in 1927, when the German scientists Selmar Aschheim and Bernhard Zondek discovered that injecting a pregnant woman’s urine into a mouse or rat would send it into heat, which could be ascertained only by dissecting the animal. Over the next few decades, the AZ test, named after its creators, replaced rodents with rabbits—the phrase “the rabbit died” was, at one point, a euphemism for a positive pregnancy test—and then frogs (so many frogs were exported from southern Africa to the U.S. for pregnancy tests, in fact, that some scientists believe they may be the source of a fungal disease currently threatening the country’s amphibian population). In the 1960s, scientists ditched the animals entirely, turning instead to immunoassays, or tests that combined hCG, hCG antibodies, and urine—if a woman was pregnant, the mixture would clump together in certain distinctive ways.

While women no longer needed a frog or a rabbit, though, they still needed a doctor. The test also frequently turned up false positives, as hCG could easily be confused for other similar hormones. A more accurate test wouldn’t arrive until 1972, when Judith Vaitukaitis and Glenn Braunstein, researchers at the National Institutes of Health, identified an immunoassay that could successfully measure levels of hCG, rather than simply detecting its presence. Recognizing the potential of their discovery, the two attempted to patent it on behalf of NIH—but were shot down by the institute’s lawyers, who argued that because the project had been funded with public dollars, nobody should receive any royalties for the resulting product. Instead, the knowledge went immediately into the public domain, until pharmaceutical companies recognized the same potential that Vaitukaitis and Braunstein had seen.

In the meantime, both scientists moved on to other things—which, according to an oral history by NIH, may have been an act of self-preservation as much as anything. To obtain enough urine for another part of their hormone research, unrelated to pregnancy tests, the scientists had struck up a deal with a nearby retirement home for nuns: The nuns would collect their urine over several weeks in plastic containers big enough to hold around 15 gallons at a time. Once a month, Vaitukaitis, Braunstein, and their colleagues—including “someone who was strong enough to lift these bottles,” Vaitukaitis recalled—would trek over to haul it all back to the lab.  

“We got a lot of stuff done with that,” she recalled, but “I would never want to do it again.”

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“The pregnancy test has a very different significance to different people,” Marcel Wanders, a product designer for a 1990 version of Organon’s test, told The New York Times in 2012. “You can’t put too much meaning into it.”

He was referring to the challenge of choosing the graphic that would appear on the test to signify a pregnancy. In the years before today’s blue lines, The Times reported, a positive result came in the form of a baby’s smiling face, a swollen belly, even a single wiggling sperm—cutesy, cheery images announcing news that, for many women, is neither cheery nor cute.

Iconographic missteps aside, though, this was the defining feature of the home pregnancy test: In the privacy of their own bathrooms, women could—to borrow Wanders’ phrasing—put their own meaning onto it, a fact that led some to protest the test’s rising popularity even as others celebrated it.

Unlike medical tests that reveal something otherwise unknowable about a body, a pregnancy test can only speed the delivery of information; regardless of who pees on what, a pregnancy has other, more obvious ways of making itself known with time. The home pregnancy test, then, wasn’t just about knowing; it was about taking charge, a sentiment that fit in nicely with the ethos of the time. The first home test approved by the FDA, Warner-Chilcott’s e.p.t. (short for “early pregnancy test,” and later for “error-proof test”), came to market in 1976, followed soon after by the Predictor and a handful of others. At that point, Our Bodies, Ourselves was six years old, and abortion had been legal in the U.S. for three.

“In many ways,” the NIH website notes, “a pregnancy test is difficult to market. The term ‘hCG’ sounds foreign and the phrase ‘urine stream’ is difficult to sugar coat.” From the beginning, advertisements for home pregnancy tests focused less on how they worked and more on what they offered—privacy, autonomy, knowledge of one’s own body. “Every woman has the right to know when she is pregnant,” read one 1970s ad for the Predictor, “and to know it with the least possible fuss and bother in the least possible time.” And a 1978 ad, this one for the e.p.t., called it “a private little revolution that any woman can easily buy at her drugstore.”

But in any revolution, even a private little one, something is being overthrown. In this case, it was the authority of doctors, not all of whom were happy about a changing status quo. Unregulated tests had already been recalled several times before the FDA approved the e.p.t, they pointed out. Tests could be used incorrectly; they could be flat-out wrong; putting them in the hands of the patients, they argued, would harm more than it would help. In an editorial published in The American Journal of Public Health in 1976, one physician argued against the use of home tests: “I feel that the reputations of both the commercial concerns and the profession of medical laboratory technology will suffer unless legislation is introduced to limit the use of such potentially dangerous kits.”

In a note following the piece, the journal’s editors sided firmly on the side of the tests: “Not everyone,” they wrote, “needs carpenters to hammer in their nails.”