Tenaliramans story is 5-6 century year old and he got blessings of maa-kaali. In dattatreya tantra, Shiva said that no mantras will work in kaliyuga except those which He mentioned in this work.
However, my question is about a sadhu who gave Tenali the mantra. Who was he? And I need some scriptural evidences of Tenaliraman which are somewhat rare ones.