Final answer:
The provided reference material does not specify the old Yogi that Madho Das met. The history of yoga includes various spiritual leaders and schools but does not detail Madho Das's mentor.
Step-by-step explanation:
The old Yogi that Madho Das met in Nasik and learned 'Tantric Science' from is not explicitly mentioned in the provided reference material. The history of yoga, including its origins and development, details significant figures and teachings that have shaped its path, such as the works of sage Patanjali and the philosophical schools like Samkhya, Yoga, and Vedanta. However, specific individuals like Madho Das and their mentors from historical accounts outside the scope of the provided texts are not covered. Hence, a precise answer cannot be given based on the provided information.