Seat Tube Interior Stops?
 

I am working on a 1991 Schwinn Crosscut bike. When I went to reinsert the seat post, I could only slide it down so far before it came to a firm stop. When I looked down into the seat post, there was what looked like a very small post protruding into the interior of the tube, clearly blocking the seat post from descending any further. I'd say it inserted about six inches leaving three inches out of the tube. But I am wanting the seat even lower. I know I can simply cut the post down, but I am curious about what I saw. Is this something common that I'm just now noticing? What is the purpose of it? Thank you.

Water bottle cage bolt?

Dang, yes, good call Rolla. Combination of freakishly long stem on the one hand and my own fatigue on the other. Thank you!