One of the many enticingly tactile manuscripts included in the exhibition Touching the Past: The Hand in the Medieval Book, curated by former Getty graduate intern Megan McNamee, is a device called a volvelle.

Zooming in on the device here is almost as satisfying as touching the real thing.

Here’s how it works: Layered circles of parchment are held together at the center by a tie, allowing the user to rotate pointers to calculate the position of the sun (Solis) and moon (Luna) at different points throughout the year. A circle with letters in red also indicates the astrological sign associated with each period.

A volvelle is a cousin of the astrolabe. Volvelles are concentric paper or parchment circles used in medieval Europe to calculate the phases of the sun and moon, while astrolabes are instruments, often made of metal, used since antiquity to observe and calculate the position of celestial bodies.

(Aside on etymology: Volvelle comes from the Latin verb volvere, to turn. It is occasionally seen spelled as vovelle, while its moving parts are sometimes referred to as rundells.)

It is remarkable that this device—which inspires so much manipulation and movement—has remained intact since its creation around 1386. This was not long after volvelles were introduced to Europe in 1274 by artist and writer Ramón Llull, who worked in the Kingdom of Majorca (present-day Spain).

Llull was a mystic philosopher (with a wicked mustache) who hoped to settle religious disputes with his first volvelle, which produced combinations of nine letters thought to represent the nine names of God. Another volvelle by Llull called “The Night Sphere” used the position of stars to calculate time during the dark hours of the night. This allowed him to suggest the most “potent” times to administer medicine according to the movement of celestial bodies.

Determining time at night was achieved through the not-so-simple process of aligning the device with a pole star; closing one eye; centering the cross of circles on the face, equidistant from both eyes; and locating another star rotating around the central star. So long as you don’t move your head or hands in the least, you could determine your place in the universe!

Revolutionary for its time, the parchment calculating device was considered a form of “artificial memory” that freed users from committing large amounts of detailed information to mind. Because of this, the device has been compared to early computers—though a comparison to a floppy disk might be more accurate. In fact, more durable tools known as astrolabes had been cast in metal in ancient Greece, and the technology was preserved in the Islamic world before returning to popular use in Europe.

However, as with any new technology, there were skeptics. Volvelles and their users were often suspected of dark magic, perhaps because of their mystical origins and their claims to predict the future. Even into the sixteenth century, numbers and measurements were given spiritual significance and supernatural potential. The eccentric individuals making use of the “secret” knowledge contained in such devices were often suspected of insidious intent. However, as scientific thought progressed, volvelles became increasingly valued not just for their ability to record information, but also for their potential to produce new knowledge.

As visitors to the volvelle currently on view may notice, access to these temptingly tactile devices often proves difficult. The high cost to produce the parchment of the volvelle in the Touching the Past exhibition limited its audience in the fourteenth century to the wealthy, scholarly elite. By the sixteenth century, advances in print technology made paper volvelles and other devices with movable parts available to a wider audience. However, the delicate pieces of paper and parchment are easily damaged or lost, relegating the delightfully movable devices behind museum glass and into rare book libraries in the twenty-first century.