The Shyama Upanishad
There is a whole class of tantrik literature going under the name upanishad, which are not, however, nearly as ancient as works such as the Chandogya Upanishad and others. These upanishads, amongst which may be numbered the example below, often contain tantrik features which are absent from the older class of Hindu literature.
They may have been composed for several reasons; to give scriptural (Vedik) authority for the revealed tantras, or, quite the reverse, to undermine Vedik orthodoxy.
Be that as it may, there is no doubt that Hinduism, for many hundred years, has followed the tantrik model with temple worship, pujas, sadhus and the rest. Orthodox Brahminism has been left to orthodox brahmins.
The following name of the short work refers to Shyama (dusky), a form of the goddess, but the content is based on the puja of Kalika.
Om Krim. In the thousand petalled lotus one may achieve the true form of the absolute, most beautiful, using three Krims, two Hums, two Hrims, Dakshine Kalike, then the previous seven syllables, ending with svaha. This is the best of all mantras.
One who recites this is lord of gods, the lord of the universe, the lord of women, every guru, all name, learned in all the vedas, immersed in all the sacred waters, Sadashiva himself.
Triangle, triangle, triangle, triangle, triangle, together with eight filamented petals, with a bhupura. Place Devi here, and in the heart and other limbs meditate on Her.
Meditate on Kalika as an adolescent, the colour of a thunder cloud, with crooked teeth, her hands bestowing boons, removing fear, and holding a sword and a head.
Kali, Kapalini, Kulla, Kurukulla, Virodhini and Vipracitta are in the six angles. Ugra, Ugraprabha, Dipta, Nila, Ghana, Balaka, Matra, Mudra and Mita are in the nine angles. Brahmi, Narayani, Maheshvari, Chamunda, Varahi, Narasimhi, Kaumari and Aparajita are in the eight petals. Madhava, Rudra, Vinayaka and Saurah are in the four angles. The dikpalas are in the directions.
Worship Devi in all the limbs, making the oblation with nectar and doing puja with the pancatattva. This is how devotees become saints.
The first result is that enemies become friends. Reciting the mantra protects against theft. The devotee becomes wealthy. This is the result of devotion to Tara, Durga or Sundari. All Bhutas sleep, while the black limbed one awakes. He without a son who studies this Upanishad of the black limbed one, gets a son. It is the equivalent of bathing in water like the Ganges, going to the holy places, sacrifice and homa.