Should Entities in Clean Architecture know of persistence mechanisms?

In the book 'Clean Architecture' (Robert C. Martin) p. 191, he states that "Entity is pure business logic and nothing else". I am unsure of how literal I should interpret this statement with respect to the entites knowledge of a persistence mechanism.

I am assuming the entity objects are stateful - that they manipulate the business data that they represent. If so, the persistence-layer must be informed of changes to that data, so it can persist those changes. Therefore; are the entities allowed to hold a reference to a persistence-interface (or a unit-of-work-interface, if a more elaborate design)?

I am inclined to think that an entity-object holding such a reference (and calling it from within the entity) would be something else than 'pure business rules'. But I have a feeling it does not count as long as the entities hold reference to an interface?

And if the entities should NOT hold reference to persistence-mechanisms, are there any other good patterns for persisting changes to business data?