I'm trying to locate the quote: And when the seven thunders had uttered their voices, I was about to write: and I heard a voice from heaven saying unto me, Seal up those things which the seven thunders uttered" and I think it was written by Italo Calvino.

The quote cannot be attributed to Italo Calvino, unless he himself was quoting the Bible.

And when the seven thunders had uttered their voices, I was about to write: and I heard a voice from heaven saying unto me, Seal up those things which the seven thunders uttered, and write them not. Revelation 10:4