On his recent trip to Saudi Arabia, President Donald Trump and Saudi King Salman were captured in a photo putting their hands on a glowing orb. The comical picture has launched a thousand jokes and memes about crystal balls.

It turns out that Trump and King Salman weren't trying to divine the future or electrocute themselves. The bizarre orb was not actually a crystal ball at all; it was an illuminated globe meant to represent the world as part of an event showcasing the Global Center for Combating Extremist Ideology.

But if it were a crystal ball, that wouldn't be so surprising, as the practice of "crystal gazing" has been common for millennia all over the world, from the British Isles to China and the Americas, wrote Andrew Lang in "Crystal Gazing: Its History and Practice, with a Discussion of Evidence for Telepathic Scrying" (The De La More Press, 1905).

From their murky origins to their history to their weirdest uses, here are five facts about crystal balls. [13 Common (But Silly) Superstitions]

Druid roots

The technical term for the act of gazing into a shiny reflective surface as a means of divining new information or predicting the future is "scrying." The term is a shortening of the word descry, and it has roots going back to the ancient Druids, part of an elite class of Celtic people who lived primarily in the British Isles and France during the Bronze Age. According to "The Natural History" by Roman-era naturalist and historian Pliny the Elder, Druids used crystals to foretell the future. Julius Caesar also described Druid superstitious practices in his oral histories of the Gallic Wars. (Caesar was waging war against the Gallic nations at the time, so he may have had reason to exaggerate some of their less savory customs, such as human sacrifice.) Druids did not limit their divination to crystals; pools of water, mirrors or reflective glass would also do.

Worldwide trend

However, crystal gazing wasn't confined to the Druids in ancient Gaul. In "Crystal Gazing," author Lang noted that the practice held sway in China as well. A Chinese criminal code from 1888 described a practice called Yuang-kuang-fuchou, or the magic of the round glittering, which a practitioner allegedly used to call up the face of a thief who may have stolen his belongings.

And the same book notes that Muslims in India practiced "viewing of unjun (lampblack or the magic mirror.)" According to research done by David Margoliouth in the late 1800s on Muslim divination, the Khalif Mansur, who lived in the eighth century, used a mirror that could allegedly reveal whether someone was friend or foe. Another legend holds that a different leader possessed a ruby ring that could reveal faces in its surface. Other folk remedies have historically included sick people looking into a shiny pot of water to be healed, as was beleived in Medina, Saudi Arabia, while other people used mirayat, or magic mirrors, according to "Magie & Religion dans L'Afrique du Nord" (1909).

Forbidden practice

While crystal gazing and scrying may have been popular throughout the world, such divination has largely been considered a forbidden occult by major world religions.

For instance, the Old Testament expressly forbids divination, saying, "for these nations, which you are about to dispossess, listen to fortune-tellers and to diviners. But as for you, the Lord your God has not allowed you to do this." (Deuteronomy 18:14). In Ezekiel 21:21, the King of Babylon (who is the enemy of the Israelites) either shuffles arrows or polishes their surfaces to read them, according to "Magic and Divination in Ancient Palestine and Syria" (E. J. Brill, 1996). The idea is that something about the appearance of the arrows could reveal insights into the future, according to the book.

The Koran also expressly forbids the pagan practice of El Meysar, a form of divination that involved shuffling arrows, along with similar practices, while the Catechism of the Catholic Church warns faithful adherents against Spiritism, which involves using divination or magical practices. In the book "The City of God," St. Augustine said scrying was "entangled in the deceptive rites of demons who masquerade under the names of angels."

Being forbidden, however, didn't mean the practices weren't popular. Crystal balls became popular as fashion accessories or to ward off evil spirits in the Middle Ages, possibly because of their association with the wizard Merlin in the King Arthur legends. Nowadays, Merlin is often depicted with a crystal ball for use in prophecy.

Queen's court

One of the most well-connected scientists in the 16th century was known to use scrying through a crystal ball. John Dee, an astronomer, scientist and mathematician who was chums with astronomy luminaries like Tycho Brahe and Nicolaus Copernicus, also served as advisor to Queen Elizabeth I. Dee turned to crystal ball gazing after traditional scientific methods of inquiry failed to produce satisfactory insights. He believed that these divination sessions could determine the "universal language of creation," which he apparently believed needed to happen so that humanity could unite before the apocalypse.

After his death, an antiques dealer found a series of manuscripts in Dee's artifacts, which were "angelic" communications from these divination sessions. Some of these accounts were published in "A True & Faithful Relation of What Passed for Many Yeers Between Dr. John Dee (A Mathematician of Great Fame in Q. Eliz. and King James Their Reignes) and some spirits" (Maxwell, 1659). The crystal globe possibly used by Dee for divination is still housed at the British Museum.

Famous crystal balls

While crystal balls are typically about the size of a grapefruit, some have been much, much bigger. The largest-known true crystal ball is housed at the Smithsonian Institution in Washington, D.C. Weighing in at 106.75 lbs. (48.42 kilograms) and spanning a whopping 12.9 inches (32.7 centimeters) in diameter, the huge orb is the largest flawless quartz crystal in the world, according to the Smithsonian Institution. The giant orb was first cut and polished in the 1800s in China, and the mineral itself may have been mined from Burma, according to the Smithsonian Institution.

Runners-up include a flawless, 11.3-inch-diameter (28.9 cm) rock crystal sphere on display in the Crow Collection in Dallas. The Dallas globe was cut during the Japanese Meiji period. The third-largest crystal ball is the rock crystal sphere of the Dowager Empress of China, housed at the Penn Museum in Philadelphia; that orb is a mere 10 inches (25.4 cm) in diameter and weigs just 49 lbs. (22 kg).

One of the world's most famous crystal balls — the Wicked Witch's crystal ball from the movie "The Wizard of Oz" — sold for $129,000 at an auction in 2001. It is made of handblown glass and is actually slightly egg-shaped, according to Jay Walker, the curator at the Walker Library of the History of Human Imagination.

The crystal balls that are typically seen in the average fortune-teller's tent, however, are made of much commoner materials; those orbs typically consist of glass, lead crystal or reconstituted quartz crystal.

Originally published on Live Science.