Yoga Sutra 1.21 the yogis are of nine kinds
For those who practise with ardent energy, it is near
They soon attain samādhi and the fruit of samādhi.
The yogin-s, who practise the four methods beginning with faith, are of nine kinds. As he explains, they are divided according to the methods which they follow, either mild or moderate or intense. Each of these classes is sub-divided into three. Progress in the application of the method may be slow, or it may be moderate, or it may be energetic, and so it is with each of the three methods without exception. For those who practise the intense methods with ardent energy, samādhi and the fruit of samādhi are near at hand.