I agree it's not cool to go out in the wilderness and just kill rattlers that aren't threatening you. But like fishshooter, I had one right in front of my house - so that's the only rattler I ever killed. Shot it with a high power pellet gun in the brain. It was just a little guy but there were way too many kids around to mess around with it.
Kinda creepy - after waiting an hour for any twitches to die down, I hung it up on a low branch of a tree where the kids could see so they could identify rattlers in the future - I was there with them the whole time and felt that this was a great chance to teach them. Except a yellow jacket ("meat bee") found it and let his buddies know. They swarmed, we left, and later there was just a bloody skin and skeleton on that damn tree and not much else.
I looked it up just now, rattlers will go 20lbs tops per the encyclopedias. I can envision a 30 pounder - but 90? No way.