Surveying pre-Gupta inscriptions, it becomes clear that the aspiration for nirvana has one recurring feature attached to it; the aspiration of the donor for the attainment of nirvana occurs when the donation is connected in some way or another to the relics or figural or non-figural representations of the historical Buddha.
The same ideas can be seen emerging in the later canonical Pali Apadana, and connect to developments in the emergence of Mahayana.