Most of the mantras have already been a Section of a Stotra or an Upanishad or simply a fullfleged Sadhana or an Anushthana and were never meant to be Utilized in isolation. Nonetheless, more than a time period, a number of the Pundits commenced compiling the mantras and formulated textbooks https://directoryrec.com/listings848000/mantra-sadhna-expert-an-overview