Many are aware about the saṃkalpaṃ which is recited during rituals like saṃdhyā vandanam, vratas etc., But there is another mantra called Mahasankalpa(pronounced Mahā saṃkalpaṃ in IAST). Sankalpa tells the place, time and purpose of doing that ritual. But Mahā saṃkalpaṃ consists of not only place but many more things like number of lokas, aṣṭa diggaj(eight elephants which carry the earth), sapta samudras present on the earth and many more in a detailed way.
This Mahā saṃkalpaṃ is usually recited in the kaḻyāṇaṃ(marriage) of devi devatas, before doing an auspicious deed like a bath in a river during auspicious occasions like pushkaras',during great yajñas' and homas etc.,
There is a brief description of universe in this mantra. Entire mahā saṃkalpaṃ remains same but in the ending, names of the region and the purpose of the deed you are doing. But the content remains the same.
What is the source of this mantra?
You can listen to the mantra here.
The mahā saṃkalpaṃ recited in the video is for holy bath in the river