P. C. Ray, History of Hindu Chemistry, v.2, 1909, pp. lix-lx, says that this Viṣṇudeva is mentioned in a MS colophon of the Rasarājalakṣmī from Benares as being court physician to King Bukka (r. 1356-1377, Vijayanagara). The MS referred to by Ray is probably that Cited in NCC v. 23 as "SB. New DC. XII. 44818." (MS #100750 in Pandit project).