Curious stone cannon

[Jim McDougall]

Amazing!!! As Nando says, just when we think we've seen it all.
I think back on the perplexing anomaly of the leather cannons of Tibet, and some of the European attempts at light, portable cannon (I think 'light' and portable eliminated their thoughts of this particular material).

In our minds we think of the powerful charge from detonating powder, and how can these cannon fashioned out of less than expected materials withstand those contained explosions. I am wondering if possibly the gunpowder used in earlier times might not have been as potent as of course more modern types.
With admittedly meager understanding of cannon and firearms I am curious.
Michael, you know I'm looking for your key insight here

Also, would these, like the smaller forms of cannon often seen which seem too small to be effective possibly be for signaling and using lesser charge?

Thank you so much for sharing this Andi! as Nando notes, another for the files. Fascinating!!!

All best regards,
Jim