He highlights the Memex’s killer feature of associative linking and how trails of links have never been implemented in the way the Memex envisioned: It is associative indexing though, that is the essential feature of the memex, “the process of tying two items together is the important thing.” Bush describes a hypertext like mechanism at this point, but most interesting from my perspective is his emphasis on a trail as a fundamental unit — something we largely seem to have lost today. […] Documents and links we have aplenty. But where are our trails?