ne plus ultra

‖ [ L., no further; ne no, not + plus more + ultra beyond. ] 1. The uttermost point to which one can go or attain; hence, the summit of achievement; the highest point or degree; the acme. [ Webster 1913 Suppl. ]

2. A prohibition against proceeding further; an insuperable obstacle or limiting condition. [ Obs. or R. ] [ Webster 1913 Suppl. ]