That was the biggest, grouchiest rattlesnake I have ever seen in California. Perhaps because I almost stepped on him, in my sandals. California rattlers are usually shy. I've never seen one coiled before. (I've heard that they get defensive when they are about to shed because they can't see as well, but his color looked pretty fresh.) After I jumped back, with great dispatch, in a spritely manner, he stayed coiled. I shot some stills, went 50 yards back to the truck to get the video camera, came back & shot some more. His tail was getting tired after a while. The rattle would slow down in exhaustion, then fire back up when I moved.
I could see him from the truck & he was still coiled when we drove away.

I was on the ground with the camera resting on my knee. I liked the more menacing look at that angle.
As you may know they are pit vipers, so they see with heat sensors as well as sight. That adds a bit of skepticism to that idea that they are testy when shedding (because their eyes are getting cloudy). I think that would need expert verification to prove it is not folk myth. Also, kids should be taught about the triangle shape of the head which is the distinctive feature of a poisonous snake. In California. Back East in TX there are water moccasins & copperheads which are not pit vipers.
When hiking it is good practice to step on top of a rock or log first, rather than stepping right over it. That way, if there is a snake hidden on the other side it gives them a chance to slither away or rattle, rather than surprising them & getting bitten.              ©J. Ansell Frazier