Full Idea
Parmenides made some approach to the doctrine of Plato in identifying Being with Intellectual-Principle [Nous] while separating Real Being from the realm of sense.
Gist of Idea
Parmenides at least saw Being as the same as Nous, and separate from the sensed realm
Source
report of Parmenides (fragments/reports [c.474 BCE]) by Plotinus - The Enneads 5.1.08
Book Reference
Plotinus: 'The Enneads', ed/tr. Mackenna,Stephen [Penguin 1991], p.357
A Reaction
The point is that for Parmenides the One is the essence of Being, but for platonists there is something prior to and higher than Being. For Plato it is the Good; for Plotinus it is a revised (non-Being) concept of the One.