The listing below are notes I took from an Terrance McKenna lecture. I'll do a commentary on this later. And, I need to go back and find a suitable source to reference, which may or
may not be the particular video of that lecture.
Biological — Death
Historical — End of culture
Psychological — Beyond ego, death of self or identity
Physical — Outer space, that which is physically beyond what we can perceive (currently, that which is beyond the cosmic horizon)