This voluntary proto-Jigsaw trap obviously blurred his vision and made him see different colors, like when you, say, press a little bit on your eyeball with anything that is not a giant needle. Of course, science demands replication, so Newton repeated the experiment several times under different conditions to test a few things, like what colors can be seen in well-lit rooms versus dark ones. We'd say it's what any sane scientist would do, but the whole notion of sane science went out the window several sentences ago.
Newton didn't have a monopoly on scientific self-harm, though. Chances are that when all those pizza rolls finally come to collect and your heart explodes, the pain that drops you to the floor will be coming from your left arm. Phenomena like this, in which the body part that's failing isn't where the pain is felt, are called referred pain, and it wasn't well understood for a long time. So in the 1930s, scientists Thomas Lewis and Jonas Kellgren decided to check it out.
Their method was as simple as it was horrifying: In order to determine which body parts would refer pain to which other body parts, they took a long syringe, filled it with saline, and then injected it into various parts of their bodies. That might not seem like a big deal, but salt water will fuck you up right quick if you inject it into the right/wrong places, like your muscle tissue. Which is exactly what they did, causing short bursts of extreme pain. When this didn't yield the data they needed, they decided to move on ... to stabbing needles right into their bones. There was a problem, however (OK, many problems): The hypodermic needle they'd been using wasn't strong enough to penetrate bone. Not to be robbed of their chance at agonizing glory, they improvised and used a metal spike made of sharpened stainless steel wire to pierce Kellgren's shin bone.
Believe it or not, this obvious excuse to engage in some collegiate S&M actually proved scientifically useful. Thanks to Kellgren and Lewis' weird kinks, doctors now have a better road map of where pain is felt and what it might mean. And to think, the only good that's ever come from our sex lives is fewer baristas getting yelled at.