In 1860, a concerned tourist wrote to the London Times decrying the “foolish, vulgar and ruthless practice of the majority of visitors” to Stonehenge “of breaking off portions of it as keepsakes.” Today, taking a hammer and chisel to a Neolithic monument seems like obvious vandalism, but during the Victorian era, such behavior was not only common but expected.
Eventually, tourists were not just taking from Stonehenge, but also leaving their mark, too. By the middle of the 17th century, tourist graffiti was appearing on the stones. The name of Johannes Ludovicus de Ferre—abbreviated “IOH : LVD : DEFERRE”—is etched, and so is the engraving “I WREN,” which may refer to Christopher Wren, the famed architect who designed St. Paul’s Cathedral.
You can read the whole article, which also gives an interesting history of Stonehenge’s ownership here on Atlas Obscura