http://en.wikipedia.org/wiki/Sankhara

Volitions /  “volitional formations” / body formations / mental formations / Plane of Causality / Conditioned Formations

Transmutation / Alchemy of Sankhara

Corequisites: concentration and striving

In most canonical discourses these four bases of power are developed in tandem with “volitional formations of striving” (padhāna–saṅkhāra).[5] For instance, in the “Concentration due to Desire” discourse (Chandasamādhi Sutta, SN 51.13), it states:

“Bhikkhus, if a bhikhu gains concentration, gains one-pointedness of mind based upon desire, this is called concentration due to desire. He generates desire for the nonarising of unarisen evil unwholesome states; he makes an effort, arouses energy, applies his mind, and strives. He generates desire for the abandoning of arisen evil unwholesome states … for the arising of unarisen wholesome states … for the maintenance of arisen wholesome states …; he makes an effort, arouses energy, applies his mind and strives. These are called volitional formations of striving. Thus this desire and this concentration due to desire and these volitional formations of striving: this is called the basis for spiritual power that possesses concentration due to desire and volitional formations of striving.”[6]

This discourse similarly analyzes the latter three bases of powers as well.