
Valmiki Ramayana (Bala Kanda 29): Penance of Lord Vishnu: Sri Rama visited Siddhashrama while travelling with sage Vishwamitra and enquired about the hermitage. Sage Vishwamitra told that it was the hermitage of Vamana avatara of Lord Vishnu. Lord Vishnu performed tapas there for hundreds of yugas (before assuming the form of Vamana Avatara).