A member of the Eton public school O.T.C. (Officers Training Corps) practising shouting out orders during a training session, 20th January 1940. (Photo by Hulton Archive/Getty Images)

A design of Hongik University Seoul is displayed on July 19, 2011 in Maranello, Italy. The Ferrari World Design Contest has been launched by Ferrari in collaboration with Autodesk for 50 prestigious international design schools. The winners will win an internship at Ferrari. (Photo by Vittorio Zunino Celotto/Getty Images)

If we were to burn NH4Cr2O7 with HgSCN in the Dark Ages in Europe and show it to anyone, it is us who would be burning next on a fiery cross of Inquisition. And it’s no wonder, since this experiment produces a truly marvelous result. At first, as you ignite the mixture of NH4Cr2O7 and HgSCN, all you can see is that it is slowly burning with a reddish flame. After a while, however, a crater is formed in the middle of the burning pile, and then, suddenly, tentacle-like appendages start sprouting from the burning mixture. And you can almost hear the scream of the mad occultist – “Come forth, Kraken! Come forth!” But of course, this is simply a chemical reaction that is called the "Pharoah's Serpent". It was also often sold in firework stores until people realized that it was toxic.

A sculpture of Don Quixote shows him wearing the basin he mistook for the enchanted helmet of the fictional Moorish king Mambrino in Alcazar de San Juan, Spain, April 5, 2016. The arid central Spanish region of La Mancha is the setting for “Don Quixote”, the seventeenth-century novel by Miguel de Cervantes. Four hundred years after his death, references to the characters of Don Quixote, his loyal squire Sancho Panza and his beautiful lady Dulcinea abound in the surrounding villages from sweet treats to theatre productions involving livestock. Cervantes did not give away the name of the birthplace of Don Quixote, a middle-aged gentleman who becomes obsessed with chivalrous ideals. But many identify the village of Argamasilla de Alba as his hometown. The anniversary of Cervantes’ death is marked on the 23 April. (Photo by Susana Vera/Reuters)

An open water swimmer surfaces as she enjoys a socially-distanced dawn swim after breaking the ice on the surface of a lake near Scunthorpe, northern England, January 9, 2021. Faced by a sharp rise in coronavirus infections, driven by the new strain, England entered a strict lockdown on January 5, 2021, with schools and non-essential shops closed for at least six weeks after previous measures failed to halt the steep rise in cases. (Photo by Lindsey Parnaby/AFP Photo)

Two displaced Tigrayan girls giggle next to their mother, left, as their photograph is taken outside the Hadnet General Secondary School which has become a makeshift home to thousands displaced by the conflict, in Mekele, in the Tigray region of northern Ethiopia Wednesday, May 5, 2021. The Tigray conflict has displaced more than 1 million people, the International Organization for Migration reported in April, and the numbers continue to rise. (Photo by Ben Curtis/AP Photo)

A pile of destroyed cars of teachers sits outside Briarwood elementary school in Oklahoma City, Oklahoma May 22, 2013. Rescue workers with sniffer dogs picked through the ruins on Wednesday to ensure no survivors remained buried after a deadly tornado left thousands homeless and trying to salvage what was left of their belongings. Curvature of horizon in the photo is due to an ultra-wide angle lens. (Photo by Rick Wilking/Reuters)