The pilcrow began its life as a letter. It grew out of a capital C, the initial of the Latin capitulum, meaning little head and, by extension, chapter. Over time the plain C gained its distinctive vertical strokes, the upright bars that give the modern mark its look, until it no longer resembled the letter it came from. In its heyday it did steady work in manuscripts, placed to mark every new paragraph, a visible signpost telling the reader that one thought had ended and another begun.

The strange part of its story is how it disappeared by being planned for. In the great age of hand-produced books, the making of a page was divided among specialists. The scribe would write the main text but leave the pilcrows out, holding open a small blank space at the start of each paragraph so that a rubricator, the craftsman who added marks in red, could come along afterward and fill each gap with a pilcrow by hand. It was an elegant division of labour, in theory. In practice, deadlines won. The rubricators fell behind, or were skipped to save time and money, and the pages went out with the spaces still empty, the pilcrows never added.

And here is the quiet transformation the exhibit loves. Readers looked at those unfilled gaps and understood them perfectly well. The empty space itself became the paragraph break, doing the pilcrow's job without the pilcrow. The mark faded out of the very role it had been invented for, absorbed into the indentation we still use today, that small blank at the start of a paragraph that says a new one has begun. The pilcrow did not so much vanish as leave its shape behind as an absence. It survives now mostly as an editor's symbol, revealed when you show the hidden marks in a document, but its true legacy is invisible: every indented paragraph is a pilcrow that was never drawn, a blank that learned to mean what the mark once did.