From Stevens' Portals in 4.4BSD paper:
"Ideas similar to portals have appeared in numerous operating systems over the past decade.
The 4.2BSD manual [Joy et al. 1983] defined the portal system call, with seven arguments, and a footnote that it was not implemented in 4.2BSD."
On a side note: what a beautiful idea Portals was. It's a shame that Linux has never caught up with BSD on it.