© Getty Images

Pope Gregory IX deemed cats evil -

Mass killings of cats reportedly followed. Really, cats (black ones in particular) have been demonized ever since.

© Shutterstock

Pope Gregory IX deemed cats evil -

But the reported cat killings may have contributed to the proliferation of rats, which consequently helped spread the plague!

© Shutterstock

'Mary Had a Little Lamb' is based on a true story -

The real person was called Mary Sawyer, and indeed she took a little lamb to school in 1816.

© Getty Images

'Mary Had a Little Lamb' is based on a true story -

A young man named John Roulstone witnessed Mary sneaking the lamb into school and wrote a poem about it. He then gave it to Mary.

© Getty Images

Human alarm clocks -

Before alarm clocks, people would pay "knocker uppers" to wake them up. They would do so by using long poles and knocking on people's windows.

© Getty Images

Human alarm clocks -

Alternatively, they used pea shooters. Sounds like a fun job, right?

© Getty Images

Heroin was used to treat children’s cough -

In the 1890s, heroin was commercialized by the German pharmaceutical company Bayer as a cough remedy.

© Public Domain

Heroin was used to treat children’s cough -

In fact, the company specifically advertised its use for children up until 1912.

© Public Domain

Swearing parrot -

President Andrew Jackson famously owned a pet parrot. When the president died, the animal attended his funeral in 1845.

© Getty Images

Swearing parrot -

However, the parrot started to swear, and mourners were obviously disturbed by it. The bird ended up having to be removed from the funeral.

© Getty Images

Sacrilegious forks -

Back in 11th-century Italy, forks were actually considered sacrilegious.

© Getty Images

Sacrilegious forks -

But why were forks offensive to God? Well, God created humans with fingers, which they used to eat, so they wouldn't need such a tool, right?

© Getty Images

Mary Shelley kept her dead husband's heart -

The English novelist, best known for writing the Gothic novel 'Frankenstein,' actually kept the heart of her dead husband in a box in her desk.

© Getty Images

Mary Shelley kept her dead husband's heart -

Shelley’s husband, poet Percy Bysshe Shelley, drowned in a boating accident when he was 29.

© Getty Images

Pope Gregory IX deemed cats evil -

In 1232, Pope Gregory IX wrote a letter called Vox in Rama (“A Voice in Rama”) to the king of Germany expressing his concerns about witches in Germany, whose rituals included cats.

© Getty Images

Romans would use urine as mouthwash -

Sure, the Romans had some dubious practices, but using urine for dental hygiene is pretty out there even for them!

© Shutterstock

Romans would use urine as mouthwash -

Though there is some method to the madness. Urine is rich in ammonia, which has stain-removing properties. Maybe the Romans were onto something after all...

© Getty Images

Peter the Great made his cheating wife feel guilty every day -

Peter the Great's wife, Catherine, cheated on him with Willem Mons. So Peter the Great not only killed him, but found a creepy way to remind his wife of her adultery.

© Getty Images

Peter the Great made his cheating wife feel guilty every day -

Peter the Great decapitated his wife's lover, put his head in a jar, and placed it in Catherine's bedroom as a reminder of her affair.

© Getty Images

Toilet meetings -

US President Lyndon B. Johnson was said to have conducted meetings on the toilet.

© Getty Images

Toilet meetings -

He had a telephone installed in the White House bathroom so he could work while sitting on the toilet.

© Getty Images

Albert Einstein could have been president of Israel -

When Israeli president Chaim Weizmann died in 1952, Albert Einstein was offered the position.

© Getty Images

Albert Einstein could have been president of Israel -

The idea came from then-Israeli Prime Minister David Ben-Gurion. Einstein eventually refused, but it makes us wonder what would have happened if he had accepted the role.

© Getty Images

A double agent was awarded by both the Allies and Axis powers -

Spanish spy Juan Pujol García worked as a double agent for both the British and the Nazis during World War II.

© Public Domain

A double agent was awarded by both the Allies and Axis powers -

García went on to be awarded the highest honor of service from both sides: the Knight's Cross of the Iron Cross by the Nazis, and the Most Excellent Order of the British Empire.

© Public Domain

Raising of Chicago -

Chicago suffered from numerous sewage and draining problems during the 19th century. So it was decided that the city level should be raised.

© Public Domain

Raising of Chicago -

Chicago streets and buildings were actually physically raised by over four feet (1.2 meter) on jackscrews during the 1850s and ’60s.

© Public Domain

Woolly mammoths were still around when the pyramids were built -

We often associate these animals with the Ice Age, but the last ones died as late as 1650 BCE.

© Getty Images

Woolly mammoths were still around when the pyramids were built -

Which means that they were still around when the Egyptians were building the pyramids. Presumably, when the last mammoth died ,the Great Pyramid of Giza had already existed for a millennium.

Sources: (Reader's Digest) (History of Yesterday)

See also: The 30 best historical destinations to visit in the US

© Getty Images