The Traditional Yoga In Bikram's Class

While the standing postures in Bikram's yoga class---in all of yoga---are mostly less than 100 years old, the 2nd half of class that happens lying and sitting is mostly filled with traditional positions from old texts of hathayoga. 8 of the 13 postures in the 2nd half of Bikram's class are from traditional hathayoga texts.
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We looked at the three best-known texts of hathayoga: the Hatha Yoga Pradipika (HYP) from about 1500, the Shiva Samhita (SS) from about 1500 and the Gheranda Samhita (GS) from about 1700.

In the standing section of Bikram's class there are two old postures: utkatasana (GS 2:27) and tadasasana, which was originally called vrikshasana (GS 2:36).

Below are the postures in the second half of Bikram's class, followed by the traditional texts in which they are instructed.

Pavanamuktasana (not in these texts)
Bhujangasana (GS 2:42) 
Shalabhasana (GS 2:39)
Purna Shalabhasana (not in these texts)
Dhanurasana (HYP 1:25, GS 2:18)
Vajrasana (GS 2:12)
Ardha Kurmasana (not in these texts)
Ushtrasana (not in these texts, though there is a posture called ushtrasana in GS 2:41 done on the belly and grabbing the ankles)
Shashangasana (not in these texts)
Janushirasana (this position was called mahamudra in SS 4:25-36 and GS 3:4-5)
Paschimottanasana (HYP 1:28-29, SS 3:109-112, GS 2:26)
Ardha Matsyendrasana (HYP 1:26-27, GS 2:22)
Shavasana (HYP 1:32, GS 2:19)

It is worth noting that all 8 of the postures, plus the 2 in the standing section, are in the Gheranda Samhita. This text was written in Bengal, the eastern Indian province where Kolkata (and Ghosh's Yoga College) is located. It seems that this text was instrumental in the development of yogic culture in the Bengal region.