"The jar having fallen on a stone and been smashed ...".[1] [Meaning on] an obstacle, a support.[2]
And Aristophanes [writes]: "instead of ballast having swallowed many lawsuits." Meaning stones; since cranes flying carry stones in their mouths for support, so as not to be run off course by the winds.[3]
Also [sc. attested is the plural] e(/rmata: "Heracles threw big ballasts into the mouth of the Ocean, so that they would be obstacles to the wandering wild animals."[4] That is, big stones.