One Perfect Number for Each Number of Digits/Historical Note

Historical Note on One Perfect Number for Each Number of Digits
The conjecture that there is One Perfect Number for Each Number of Digits was made by in his, published some time around the $2$nd century.

It was a simple extrapolation from the knowledge of the perfect numbers at the time.

Some sources suggest that made these conjectures, but, as it is believed that  already knew the $5$th perfect number to be $33 \, 550 \, 336$, this cannot be correct.