Me for the thrift stores and looking for all the cotton sheets I can get my hands on. Thankfully they all have labels that tell the fibers, so will keep on getting what I can of them.
Some of the finest feeling ones can be a thick, fine cotton OR a cotton/poly blend, at first glance they look identical. Have to be careful about this. But I'll admit that I, myself use a pretty cotton/poly blend quilt on my own bed. I don't smoke nor do my cats, so that hazard is not bothering me.