One piece of physical evidence sometimes brought into the case for a Slavic oak and thunder cult connected to Perun is archaeological rather than textual: a large oak trunk recovered from the bed of the Dnieper River near the island of Khortytsia, with several boar jawbones embedded into it in a deliberate arrangement, radiocarbon dated by researchers to sometime around the seventh or eighth century CE, well before the events the Primary Chronicle records under Vladimir.
Soviet-era and later Slavic archaeologists, prominently Boris Rybakov among them, have proposed reading the submerged oak as a votive object connected to a thunder-god cult, pointing to the oak's independently attested association with Perun in later folklore and place-names, and to the boar's own separate association with thunder deities in neighbouring Baltic tradition, where Perkunas, a name etymologically related to Perun, is likewise linked with oaks. This interpretation remains a proposal rather than a certainty: the oak carries no inscription or unambiguous religious marking, and its interpretation depends on connecting several separate strands of comparative and later evidence to a physical object whose original ritual purpose, if it had one, cannot be recovered directly from the wood itself. It is included here not as settled fact but as an example of the kind of indirect, inferential evidence, an old tree with animal remains driven into it, pulled from a river with genuine historical associations with pre-Christian Slavic religious life, that scholars must work with in a field where, as with so much of Slavic paganism, no contemporary written account from within the tradition itself survives to confirm what such an object meant to the people who made it.