Ashoka is one of the best epigraphically attested rulers of ancient India: his edicts, carved into rock faces and stone pillars across the subcontinent, survive as contemporary, independently datable documents in his own name, and several of them list the Buddhist missions he dispatched to named regions and rulers. That corroboration, unusually strong for a figure of this period, is exactly what is missing for Sanghamitta specifically. No surviving edict names a daughter, and none describes a mission to Tamraparni, the ancient name for Sri Lanka, in the terms the chronicle tradition later gives it.
Sanghamitta's entire documented existence instead rests on the Dipavamsa and the more literary Mahavamsa, Sri Lankan Pali chronicles compiled by Buddhist monks in the fourth to sixth centuries CE, a gap of several hundred years from the events of the third century BCE they narrate. That gap does not make the account false; oral and monastic transmission of institutional founding narratives was a serious undertaking in this tradition, and the physical continuity of the Bodhi tree at Anuradhapura is real and independently observable regardless of who is credited with bringing it. But it does mean her historicity rests on a different evidentiary footing than her father's, which is the same distinction this atlas draws for Wei Huacun in Shangqing Taoism: a documented institutional founding, asserted confidently by the tradition that inherited it, without the external, contemporary corroboration that would settle the question independently of that tradition's own telling.