Matsya Purana — Description of Gomedaka and Puṣkara Dvīpas; the Lokāloka Boundary; Ocean Tide...
तथा ह्यालोक आकाशे परिच्छिन्नानि सर्वशः पात्रे महति पात्राणि यथा ह्यन्तर्गतानि च //
tathā hyāloka ākāśe paricchinnāni sarvaśaḥ pātre mahati pātrāṇi yathā hyantargatāni ca //
So indeed, within the luminous sky (the expanse of light), all things appear as though bounded on every side—just as smaller vessels, though distinct, are contained within a single great vessel.
It uses a containment analogy: even when many forms seem separate and bounded, they exist within a larger cosmic ‘container’—a perspective often used to explain how worlds can be withdrawn (dissolution) into a subtler, overarching reality.
By stressing that apparent separateness exists within a greater order, it supports the Purāṇic ethic of restraint and stewardship: a king or householder should govern possessions and duties as ‘contained’ within dharma and cosmic law, not as isolated personal ownership.
Though not a direct Vāstu rule, the imagery of vessels-within-a-vessel parallels Vāstu thinking about nested spaces (garbhagṛha within the temple body, precincts within enclosures) and ritual containment (kalasha as a microcosmic container).