I don't think it's like stoning the devil, but the reverse... Mercury, the messenger god who carries messages up to the more primary gods, and their messages / portents back to people, was portrayed with winged feed to connote speed. From there he grew into the god of travel. I think the essence was to improve the road by taking the bumps out. Throwing the rock was more about having a cairn boasting how many worshippers made such improvements.
But I could be wrong.
In any case, have you found a secular source saying that Mercury worship involved stone throwing? I tried and both Google and GPT-5 failed me.
I don't think it's like stoning the devil, but the reverse... Mercury, the messenger god who carries messages up to the more primary gods, and their messages / portents back to people, was portrayed with winged feed to connote speed. From there he grew into the god of travel. I think the essence was to improve the road by taking the bumps out. Throwing the rock was more about having a cairn boasting how many worshippers made such improvements.
But I could be wrong.
In any case, have you found a secular source saying that Mercury worship involved stone throwing? I tried and both Google and GPT-5 failed me.
No, I haven't seen any secular source about it.