Historians who opened a small copper box that been hidden in the head of a lion statue atop a Boston building for more than a century got a small surprise: a hardcover book.

In addition to the expected papers, the Bostonian Society on Thursday found the small red book inside the box roughly the size of a modern shoebox. The book had no visible markings, and nothing was taken out of the box because of the items' fragile condition. So, the contents of the book remain a mystery.

Society President Brian LeMay said he was "absolutely delighted" by the discovery.

The time capsule has been sealed inside the lion's head since 1901. Rumors of its existence were confirmed last month when the statue was taken down from the Old State House for refurbishing.