The topics treated of in the Tantras are divided into Kriyâ (ritual), Caryâ (apparently corresponding to Vinaya), Yoga, and Anuttara-yoga. Sometimes the first three are contrasted with the fourth and sometimes the first two are described as lower, the third and fourth as higher. But the Anuttara-yoga is always considered the highest and most mysterious.[324] Târanâtha says[325] that the Tantras began to appear simultaneously with the Mahayana sûtras but adds that the Anuttara-yoga tantras appeared gradually.[326] He also observes that the Âcârya Ânanda-garbha[327] did much to spread them in Magadha. It is not until a late period of the Pâla dynasty that he mentions the Kâlacakra which is the most extravagant form of Buddhist Tantrism. This accords with other statements to the effect that the Kâlacakra tantra was introduced in 965 A.D. from Śambhala, a mysterious country in Central Asia. This system is said to be Vishnuite rather than Śivaite. It specially patronizes the cult of the mystic Buddhas such as Kâlacakra and Heruka, all of whom appear to be regarded as forms of Âdi-Buddha or the primordial Buddha essence. The Siddha named Pito is also described as the author of this doctrine,[328] which had less importance in India than in Tibet. On the other hand Târanâtha gives us the names of several doctors of the Vinaya who flourished under the Pâla dynasty. Even as late as the reign of Râmapâla (? 1080-1120) we hear that the Hinayanists were numerous. In the reign of Dharmapâla (_c_. 800 A.D.) some of them broke up the great silver image of Heruka at Bodh-Gaya and burnt the books of Mantras.[329] These instances show that the older Buddhism was not entirely overwhelmed by Tantrism[330] though perhaps it was kept alive more by pilgrims than by local sentiment. Thus the Chinese inscriptions of Bodh-Gaya though they speak at length of the three bodies of Buddha show no signs of Tantrism. It would appear that the worship celebrated in the holy places of Magadha preserved a respectable side until the end. In the same way although Tantrism is strong in the literature of the Lamas, none of the many descriptions of Tibet indicate that there is anything scandalous in the externals of religion. Probably in Tibet, Nepal and mediæval Magadha alike the existence of disgraceful tantric literature does not indicate such widespread depravity as might be supposed. But of its putrefying influence in corrupting the minds of those who ought to have preserved the pure faith there can be no doubt. More than any other form of mixed belief it obliterated essential differences, for Buddhist Tantrism and Śivaite Tantrism are merely two varieties of Tantrism.