pramana viparyaya vikalpa nidra smrtayahYoga Sutras of Patanjali, 1.6
pramana = right knowledge
viparyaya = misconception
vikalpa = imagination
nidra = sleep
smrtayah = memory
This one is naming the 5 kind of thoughts mentioned in the previous sutra. The following sutras will go into more detail about what each one is.
If you want to get out of compelling thoughts, throughout the day (or during meditation) you can notice which one your thoughts fall into.
Today I noticed I was thinking about making a retreat centre in the country side and thinking about where it should be and imagining all these little huts with different colour umbrella shaped roofs like those paper umbrellas that you get in cocktails and actually open and shut (I really love them!).
So this one is mainly imagination but the umbrella part is memory and maybe about longing for a time in childhood when I was so happy playing with those umbrellas.