Your a magnet because the spot where you are sitting is either on the way to where the snakes go to hibernate or it is where they hibernate. I have worked with snakes my whole life. This is the time of the year when the snakes (especially rattlesnakes) rush to there wintering holes. It could be that there is some kind of underground cavaran under some rocks or something. to see two rattlesnakes in the same area and traveling at this time of the year is usually a good sign that your in there wintering area, check the spot in the spring and if there in there again its cause there coming out. Its not uncommon to find a hundreds of them traveling to an area where they hibernate.