Step 1: Understanding the Concept
The question asks to identify which of the given texts is not considered a text on architecture. This involves knowing the primary subject matter of each text.
Step 2: Analyzing the Texts
(A) Śilpaveda: This is an Upaveda (auxiliary Veda) and is the foundational text concerning 'śilpa' (arts, crafts, and architecture). It is definitely a text on architecture.
(B) Yajurveda: This is one of the four primary Vedas. Its main focus is on the liturgy, prose mantras, and procedures for performing 'yajnas' (sacrificial rituals). While it contains the Śulbasūtras, which describe the geometric construction of fire altars, its primary subject is not architecture but religious ritual.
(C) Arthaśāstra: This is a treatise on statecraft and political economy. However, it contains significant and detailed chapters on architecture relevant to the state, such as city planning, fortification, and construction of public buildings. It is considered an important source for secular architecture.
(D) Mānamayukha: This is a classical text belonging to the Vastu Shastra or Śilpaśāstra tradition, dealing specifically with the principles of architecture.
Step 3: Final Answer
Comparing the options, the Śilpaveda and Mānamayukha are explicitly texts on architecture. The Arthaśāstra contains major sections on architecture. The Yajurveda's primary focus is ritual, and it is not a text *on* architecture, even though it has some content related to construction. Therefore, Yajurveda is the correct answer.