percepti

Percepti is what the senses do before the mind gets involved: light hits the eye, a smell reaches the nose, and you perceptas it. It sits a step above senti, to feel, and a step below kompreni, to understand. Rimarki is the nearest neighbour and the one to reach for in ordinary speech, since it means to notice; percepti keeps a faintly scientific tone, the word a psychology textbook would use.

The seam that is not there is per plus cepti. Per is a real and very common Esperanto preposition, so the eye lands on it immediately, and there is even a per genuinely buried in the Latin. But cepti is not a word. You cannot conjugate it, you cannot build on it, and there is no family of -cepti verbs to join. Percept- is one root, borrowed entire.

Test it the way you should test every suspected compound: pull the pieces apart and see whether both halves survive on their own. Per survives, cepti does not, so there is no compound. That single check will save you inventing a dozen words a month.