[Campion]

I'd heard of this book, but I didn't realize it was online now: The Tomb of St. Peter, by Margherita Guarducci

If you scroll down a ways (quite a ways), you'll find one of the more interesting bits of evidence: on a tomb, in the Vatican necropolis near (what is believed to be) St. Peter's tomb, is the inscription:

Peter, pray for the holy Christian men buried near your body

The tomb dates no later than AD 192.

[Diego1618]

St. Peter's Tomb