“There is the case where the monk Moggallāna develops the base of power endowed with concentration founded on desire & the fabrications of exertion, thinking, ‘This desire of mine will be neither overly sluggish nor overly active, neither inwardly constricted nor outwardly scattered.’ He keeps perceiving what is in front & behind so that what is in front is the same as what is behind, what is behind is the same as what is in front. What is below is the same as what is above, what is above is the same as what is below. (He dwells) by night as by day, and by day as by night. By means of an awareness thus open & unhampered, he develops a brightened mind.”—-SN 51.14
This passage describes how progress in meditation results from attaining balance of mind through countering excessive tendencies in opposite directions with their antidotes over a period of time. “Inwardly constricted” refers to sloth and torpor, and “outwardly scattered” the sensual desire common in materialist society. The antidote for sloth and torpor is the meditation subject “light,” and in modern context this would include the Impressionist idea of painting or comprehending the light that falls on a subject.
Practising the focus on spatial directions would be an effort to control a mind outwardly scattered by reflecting that impermanence applies to objects in all directions and realms.
Fabrication of exertion: MN 101
In Buddhist terms ‘continuity’ means the illusory effect produced by not seeing impermanence and is the opposite of what is meant in the sutta by meditation on directions.
In the third foundation of mindfulness these present two negative qualities occupy the central position in the eight pairs of mind states, and overcoming them marks the ability to attain balance which allows entry to the higher states of mind:
“The ability to balance the mind, by avoiding both contraction and distraction, is an important skill required for the development of deeper levels of concentration or insight. The placing of these two states of mind at this point in the instructions for contemplation of the mind indicates the need to cultivate such balance, once one has at least temporarily moved beyond the reach of the grosser types of mental unwholesomeness and is aiming towards the development of “higher” states of mind, such as are described in the remainder of this satipatthãna.”—-Analayo