The analytical formation of the plus quam perfectum

Salvete omnes. Legi in Quora plusquamperfectum creatus esse analytico modo, cum participio et verbo “esse”. Is qui hoc scripsit est vir doctissimum quem magnopere admiror. Declarat ille participium adhibitum esse, exempli gratia : , cf. *kantāu̯osis esās > *kantāu̯isās > cantāverās . Nusquam tandem possum ipsa invenire librum vel scriptum quiddam ubi hoc explicetur. Noviste, doctissimi magisti, an hoc verum sit et ubi possum hoc legere? Gratias maximas vobis ago et quaeso, ignoscite mihi menda mea.

Good evening, everyone. I read in Quora that the plusquamperfectum was created analytically- as affirmed by a very learned man whose knowledge I admire- who says that the participle was used to create that tense, for example : , cf. *kantāu̯osis esās > *kantāu̯isās > cantāverās . Have you ever hear or read about this? I scoured different book of historical latin grammar but I couldn’t find anything. Thank you very much and sorry for my mystakes

Hello,
I don’t have as much information as you about this, but I can confirm the general idea, which is the perfect stem + the imperfect of the verb esse. Same with the subjunctive perfect and the future perfect.

My source about this is Morphologie Historique du Latin, by Ernout, an old but still relevant work.