Eusebius of Caesarea (AD 260/265 – 339/340) in his work Church History (Book V, Chapter 20 "The Writings of Irenaeus against the Schismatics at Rome") said:
Irenaeus wrote several letters against those who were disturbing the sound ordinance of the Church at Rome. One of them was to Blastus On Schism; another to Florinus
and then Eusebius cites the letter:
These things being told me [Irenaeus] by the mercy of God, I listened to them attentively, noting them down, not on paper, but in my heart.
The same passage in Greek (Source):
[5.20.7] ταῦτα καὶ τότε διὰ τὸ ἔλεος τοῦ θεοῦ τὸ ἐπ' ἐμοὶ γεγονὸς σπουδαίως ἤκουον, ὑπομνηματιζόμενος αὐτὰ οὐκ ἐν χάρτηι, ἀλλ' ἐν τῆι ἐμῆι καρδίαι·
- What media did Irenaeus use to write those letters?
- How was the media preserved for Eusebius to quote them two hundred years later?
Irenaeus (130–202 AD) could not have written on paper which was invented much later? What media had Irenaeus used to write his letters? Where could the letters be stored for almost two hundreds year until Eusebius got them?
The obvious answer to some of the above questions would be to say that Irenaeus used/refered to papyrus. But taking in mind that:
it was rather expensive and unreliable material since "papyrus was replaced in Europe by the cheaper, locally produced products parchment and vellum of significantly higher durability in moist climates"
it appears that it was not widely used for taking notes since "until the middle of the 19th century, only some isolated documents written on papyrus were known, and museums simply showed them as curiosities"
I find this answer doubtful.
First I would like to thank everyone for answering my question. Nevertheless, let me once again emphasize that "Irenaeus refered to papyrus" is not the answer I'm looking for (see above).
The age of "ancient papyrus" can hardly be determined precisely today. Recent article in Nature Scientific Reports concludes:
As we can infer from the studies of the aged reference paper samples, the effect of artificial aging cannot be told apart from the effects of natural ageing by the methods used by us.
And since "until the middle of the 19th century, only some isolated documents written on papyrus were known" we can only be sure that papyrus can survive ~200 years in modern museums (between glasses, with air-conditioning, modern chemistry etc).