The sitting posture described here (in SB 4.6.38) is called virasana according to the system of astanga-yoga performances

Expressions researched:
"The sitting posture described herein is called vīrāsana according to the system of aṣṭāṅga-yoga performances"

Srimad-Bhagavatam

SB Canto 4

The sitting posture described herein is called vīrāsana according to the system of aṣṭāṅga-yoga performances. In the performance of yoga there are eight divisions, such as yama and niyama—controlling, following the rules and regulations, then practicing the sitting postures, etc.

SB 4.6.38, Translation and Purport

His left leg was placed on his right thigh, and his left hand was placed on his left thigh. In his right hand he held rudrākṣa beads. This sitting posture is called vīrāsana. He sat in the vīrāsana posture, and his finger was in the mode of argument.

The sitting posture described herein is called vīrāsana according to the system of aṣṭāṅga-yoga performances. In the performance of yoga there are eight divisions, such as yama and niyama—controlling, following the rules and regulations, then practicing the sitting postures, etc. Besides vīrāsana there are other sitting postures, such as padmāsana and siddhāsana. Practice of these āsanas without elevating oneself to the position of realizing the Supersoul, Viṣṇu, is not the perfectional stage of yoga. Lord Śiva is called yogīśvara, the master of all yogīs, and Kṛṣṇa is also called yogeśvara. Yogīśvara indicates that no one can surpass the yoga practice of Lord Śiva, and yogeśvara indicates that no one can surpass the yogic perfection of Kṛṣṇa. Another significant word is tarka-mudrā. This indicates that the fingers are opened and the second finger is raised, along with the arm, to impress the audience with some subject matter. This is actually a symbolic representation.