Message: The night before the Battle of Milvian Bridge, Constantine sees a Chi-Rho overlaying the setting sun, with in hoc signo vinces, “In this sign, prevail,” inscribed beneath the symbol. Constantine orders soldiers to paint crosses on their shields.
Result: After winning the battle and becoming sole ruler of the Roman Empire, Constantine ends the persecution of Christians and becomes a convert himself.
Message: A man dressed in red appears to Napoleon in Egypt, telling the general he has ten years to enjoy his victory. The man visits again before Napoleon’s planned 1812 invasion of Russia, predicting a dire outcome.
Result: Napoleon goes ahead with the campaign but loses half a million soldiers and his empire.
Ghent, Belgium, 1861
Message: While trying to understand the molecular structure of benzene, German chemist Friedrich August Kekulé dozes off in front of a fire and dreams of a snake biting its own tail.
Result: The snake proves a good analogy for benzene’s ringlike structure. The insight allows for greater manipulation of the compound and the expansion of the German chemical industry.
Swimming Across the Pedernales
Washington, DC, 1968
Message: Toward the end of his first full term, President Lyndon B. Johnson has a recurring nightmare: he is swimming across a Texas river but unable to reach the shore.
Result: In a televised speech on March 31, 1968, LBJ says, “I shall not seek, and will not accept, the nomination of my party for another term as your president.” His nightmares stop recurring.
Eye of a Needle
Cambridge, MA, 1844
Message: Machinist Elias Howe dreams he is captured by cannibals in a strange land. He notices that the spears carried by the warriors are pierced near the tip.
Result: The dream provides inspiration for a better sewing-machine needle; Howe’s lockstitch sewing machine revolutionizes garment manufacturing.
England & Normandy, 1066
Message: Halley’s comet appears for the first time since 989. King Harold II, the Anglo-Saxon ruler of England, believes it a bad omen, but William, duke of Normandy, calls the comet “a wonderful sign from heaven.”
Result: William gathers troops and invades. Harold is defeated at the Battle of Hastings, and the Normans gain control of England.