Lucinda Ramberg in The Wire:
One day the jogatis took me to the river for a puja. Mahadevi came to our door early in the morning, saying: “Today we are taking the devi to the river – will you come along?” My research assistant Jyoti and I had gone roaming with the jogatis before, traveling from farmhouse to farmhouse for household rites on auspicious occasions such as the birth of a female buffalo calf or the successful drilling of a new bore well. This time, for the festival of the river goddess, we climbed in a flat bed truck trailing a big green tractor. The two traveling devis – Yellamma and Matangi – had been placed in the front of the truck. Along the way, a bumpy ride over the pock marked roads characteristic of this sugar cane-rich and infrastructure-poor district in Northern Karnataka, I asked Mahadevi whose tractor we were traveling in. She pointed to the landlord farmer swaying in the tractor seat next to the driver and explained that he and his wife were without children, despite several years of marriage, so he had decided to sponsor the bringing of the devi to the river.
I recognized in this account the making of a harake in which devotees seek to secure blessings of fertility and prosperity from the devi through acts of propitiation towards her. Devotees make material or bodily offerings such as grain, saris, silver ornaments, pilgrimages, prostrations, renunciations, or ecstatic performances. As persons who are given, or who give themselves to the devi in fulfillment of harake, jogatis themselves take the form of such offerings. Their dedication to the devi is conducted as a rite of marriage to her. This marriage authorizes them to perform rites in her name, such as the one in which we were brought to participate that day at the river Krishna.
More here.