Infinity is represented by the symbol ∞, a sign introduced by John Wallis in 1655 in his treatise, “De sectionibus conicus.” Historians believe that Wallis, a classical scholar, adopted the sign from the late Roman symbol for “1,000.” Whether it was from there or another source, the result was (and remains) the same: “a figure-eight on its side,” as many people call the infinity symbol.