I am grateful to have studied the art of yantras with Pieter Weltevrede & Mavis Gewant. (mela.yoga)
Mash this with a thick ladle or a potato masher (traditionally, a puran yantra or puran masher is used for this). (happyandharried.com)
In the complete system, these are followed by 25 positions, called yantras, with two variations of each for a total of 75 movements divided into five groups. (yogajournal.com)