Indian thinkers were well aware of the fact that its outer spatial and temporal boundaries might have not been the same as its ideal boundaries. The end (anta) of a sacrifice was not necessarily the same as its completion and the sacrificer should be aware of it, in order to avoid reaching the temporal end of the sacrifice before having reached its completion.
The latter is called saṃsthā, which is an interesting term, meaning at the same time "completion" and "form". In later texts, each sacrifice may have more than one saṃsthā (form) and the various saṃsthā are distinguished because of their completing formulas. In the Śrauta Sūtras, the meaning of "completion" prevails. Lilian Silburn, in her well-known Instant et cause writes that
saṃsthā designates [perhaps because it delimits it] the very structure of the sacrifice (p.60).Silburn further notes that saṃsthā is the temporal foundation of a sacrifice, whereas pratiṣṭhā is its spatial foundation (see also Thite, Sacrifice in the Brāhmaṇa-Texts, 1975: 274):
saṃsthā consists of a coordination of structures within time, [since] rūpa, the form, is considered to be tantamount to an activity (karman) (p.61).
It might be interesting to note that "temporal" refers to the dynamic aspect of the sacrifice, rather than to its diachronic dimension. The historical dimension of rituals and of their evolution is, by contrast, completely out of sight.