Payovrata is the vrata or penance observed by Goddess Aditi to propitiate Lord Vishnu.
Ritual Activity 
It is usually observed for 12 days, and during that time the devotee subsists on a diet of milk alone. 
In Hindu Mythology 
A notable event is that of Sage Kashyap who asked his wife, Aditi, to use this method to please Lord Narayana so that a solution could be found for her son who was defeated by the Asuras. This penance finally resulted in the Vamana Avatar sending Mahabali to the netherworld.