century BCE, starting about the same time as the Brahmana layer of the Vedas were composed and most ritual sutras were complete by around 300 BCE. They were attributed to famous Vedic sages in the Hindu tradition. These texts are written aphoristic sutras style, and therefore are taxonomies or terse guidebooks rather than detailed manuals or handbooks for any ceremony. The Śrautasūtras differ from the smārtasūtra based on smṛti (that which is remembered, traditions). The Smartasutras, in ancient vedic and post-vedic literature, typically refer to the gṛhyasūtras (householder's rites of passage) and sāmayācārikasūtras (right way to live one's life with duties to self and to relationships with others, dharmaśāstras). Śrauta Sutras The Śrautasūtras form a part of the corpus of Sanskrit sutra literature. Their topics include instructions relating to the use of the śruti corpus in great rituals and the correct performance of these major vedic ceremonies, are same as those found in the Brahmana layers of the Vedas, but presented in more systematic and detailed manner. Baudhayana srautasutra is probably the oldest text in the śrautasūtra genre, and includes in its appendix a paribhāṣāsūtra (definitions, glossary section). Other texts such as the early Apastamba śrautasūtra and later composed Katyayana start with Paribhasa-sutra section. The śulbasūtras or śulvasūtras are appendices in the śrautasūtras and deal with the mathematical methodology to construct geometries for the vedi (Vedic altar). The Sanskrit word śulba means "cord", and these texts are "rules of the cord". They provide, states Kim Plofker, what in modern mathematical terminology would be called "area preserving transformations of plane figures", tersely describing geometric formulae and constants. Five śulbasutras have survived through history, of which the oldest surviving is likely the Baudhayāna śulbasūtra (800-500 BCE), while the one by Kātyāyana may be chronologically the youngest (≈300 BCE). Rituals Śrauta rituals and ceremonies refer to those found in the Brahmana layers of the Vedas. These include rituals related to fire, full moon, new moon, soma, animal sacrifice, as well as seasonal offerings made during Vedic times. These rituals and ceremonies in the Brahmanas texts are mixed and difficult to follow. A clearer description of the ritual procedures appeared in the Vedanga Kalpa-sutras. The Vedic rituals, states Burde, can be "divided into Śrauta and Gṛhya rituals". Śrauta rites relating to public ceremonies were relegated to the Śrautasutras, while most Vedic rituals relating to rites of passage and household ceremonies were incorporated in the