How they used to get rid of motor oil back in the day.

"Feed a cold, starve a fever." Rest, hydrate, and eat if you can.

Aristotle was obviously a great teacher and philosopher but he ended up being wrong about a lot. Like he thought the “elements” were earth, wind, fire, and water and that all objects want to be in their “natural” place. So, if you drop a rock, it tries to return to the earth. Fire goes up because it’s trying to get to where it “wants” to live.

He thought eels didn’t procreate because no one had ever seen it happening. (They go out to sea to fuck.) He was into bees and correctly noticed that there were workers and drones and that young bees grow out of the honeycomb. But he just assumed the Queen was a King and that worker bees were out collecting tiny baby bees from flowers. (He thought the air just blew pollen around and the honey naturally appeared.)

He had a lot of ideas that were just ideas but he was so influential and his writings were preserved and translated. It took a shocking number of years for people to question if Aristotle was full of shit.

Check out the history of bird migration science. There was everything from birds going to the moon for winter, swallows burrowing in the mud, transmorphing to different species, up to the 19th century

Lightning never strikes the same place twice. In fact it favors repeated strikes at the same arcing point.

In the middle ages churches would ring the steeple bells during a thunderstorm in an effort to soothe God. (it was assumed the Christian God was directly responsible for lightning.) This resulted in such an epidemic of lightning deaths among parish priests that ringing church bells in thunderstorms remains a criminal act in some regions of Europe.

Modern cathedrals and statues are fitted with replaceable lightning rods, in an admission God is content to let the mechanics of static electricity guide His thunderbolts.

Classic case of survivorship bias

People back in the day had just as much terrible advice as we have today, it's just that the only one that survived long enough to survive to the present day is the really good advice

But to answer the question, anything related to the ingestion of mercury

witch burning

Its perfectly safe to burn any and all trash

Especially batteries

Phlogiston, its where heat comes from!

https://en.m.wikipedia.org/wiki/Phlogiston_theory

Babylonian astronomy

https://en.m.wikipedia.org/wiki/Babylonian_astronomy

HEAD ON APPLY DIRECTLY TO THE FOREHEAD!

The Ether/Aether

That there is an invisible structure all around us that allows gravity, light and electricity to move through it. Now debunked or replaced.

Trepanning to release evil spirits.

Drill a hole in your head as a cureall for any mental behaviour abnormalities. Still practised as an emergency surgery, only to release life-threatening blood and pressure buildup inside the cranial cavity.

Blowing smoke up your ass

Gut pain? Almost drowned? Time to blow some tobacco smoke up your bum. Discontinued.

The bible.

Medicine and not taking anything as the will of god you should just accept, this and perception of death. That direct war, colonies are necessary - because now soft power, investments, influence, proxies are seen as more effective and better for business. That raw physical fitness means an easy superiority - and not a gun. Slavery and serfdom took other forms, so are associated stereotypes. Talking while seemingly alone is, arguably, not a solid sign of a mental illness now. First paleness became no longer a wanted trait, then we learnt that sun tan can be bad too. Putting fire to a field or a property isn't a good idea like it was before. Natural resources are free, limitless and harvested with no consequencies. Finding a stash of gold isn't that tempting too. Mass production, services kind off changed the amount of skills one needs in an average household and added complexity to it. Knowledge of how to get a clean water noticeably changed our ways. And perception of sex and family in different cultures drastically changed over time due to religion, law and science.

Drowning women to determine if they are witches.

That there is a god (or gods)

Whatever you do, don't ask for bloodletting if you get sick

Anyone reading this thread and genuinely interested in it should go listen to the dollop podcast. It's American history, mostly between the 1500's and now. But the different episodes they do are stuffed full of this kind of faulty logic from the past.

Blood letting. Have a fever, must be to much blood inside you.

What goes up comes back down.

Apply math and the object flies in a parabolic arc (not accounting for air friction and wind)

Launch it high enough and the arc start looking elliptical. Gravitational force looks less like a constant rather is tempered by distance². If the acceleration closes the ellipse without hitting the (circular at this scale) ground, your object is now a satellite in orbit.

Keep accelerating and eventually (a whole lot of acceleration) and special relativity factors affect the trajectory...and mass...and time dilates between the object and observers.