This chapter argues that literary accounts of visions in some Mahāyāna sources (often referred to as samādhis) possess characteristics that are strikingly similar to reports of actually visionary experiences that individuals have undergone while their psychologies and physiologies were profoundly altered in some way. Moreover, some of the methods used to induce actual visions also parallel methods recommended or described in some Mahāyāna sūtras. These parallels are strong enough to suggest that visionary altered states of consciousness formed an experiential basis for the emergence of new Mahāyāna sūtras, which contributed to the imaginative restructuring of Buddhist cosmology found within Indian Mahāyāna Buddhism.