Ashtanga is hard. Students come together in a school/room, called a shala, and do a series of poses. Instead of calling out the poses, the teacher individually instructs each student on the postures and the order they are done. When practiced this way, it’s called Mysore-style, after the city where guru Pattabhi Jois has his shala. Ashtanga is also practiced as a class (though not traditionally).
The series are memorized by daily practice, usually early morning, rather than reading about them or writing them down. As each student moves through the series at her/his own pace, the teacher walks around, teaches, and corrects. First the primary series is learned, and when that is mastered, the secondary, and so on.
Ashtanga was created by Krishnamacharya for his student, Pattabhi Jois (featured in youtube link above). Krishnamacharya taught the three Indians whose styles of hatha yoga have had the biggest impact internationally: P. Jois, B.K.S. Iyengar, and T.K.V. Desikachar.
Many Ashtangis, including Jois, claim that the series of postures weren’t created by Krishnamacharya but are ancient and were outlined in the Yoga Korunta, which no longer exists. The lore is that this ancient text was written on palm leaves, and after Krishmacharya learned it, the leaves were eaten by ants (source: Enlighten Up!).
It’s argued by others that the system isn’t ancient at all, and that sun salutations were adapted from Indian martial tradition in the late 1800s, when the Hindu masculinity movement was strong (Joseph S. Alter, Yoga in Modern India).
I imagine the truth in somewhere in the middle. Yoga postures have been done for hundreds, if not thousands, of years. The seminal text on physical yoga is the Hatha Yoga Pradipika, written in the 15th Century, and texts on yoga as a classical philosophy existed before the Common Era. (Yoga is not simply physical postures and breathing exercises. This is only hatha yoga, a bit part of yoga, one of the six classical systems of Indian philosophy.) Edwin Bryant, a scholar of Yoga and Hinduism at Rutgers, believes that, “The origins of yoga are in primordial and mythic times.” I like this. Yet physical yoga as we know it, even the more traditional schools taught by Indian gurus who demand a certain orthodoxy, is certainly a very modern phenomenon.
Because of this orthodoxy and the intensity of the practice, Ashtanga attracts some interesting people. Ashtanga Lanka was founded by Fred Lewis, a once-hippie septuagenarian from California. He bought a guesthouse in Sri Lanka ten years ago and expanded it. About five years ago he added the shala (yoga room/school). He brings in a teacher when he’s there for the tourist season from November through March, and lives in California during the off-season.