Besides the advice already given there are four postures, Sitting, Standing, Walking, and lying down.
so maybe experiment with the each?
as already mentioned the sitting posture doesn't need to be done crossed legged, you can use a cussion or stool to support your weight, or even a chair, but if you decide to buy one shop arround you don't wan't to buy a £70 bench to find a £35 one later which is just as good for a trial purpose.
He who knows only his own side of the case knows little of that. His reasons may be good, and no one may have been able to refute them.
But if he is equally unable to refute the reasons on the opposite side, if he does not so much as know what they are, he has no ground for preferring either opinion …
He must be able to hear them from persons who actually believe them … he must know them in their most plausible and persuasive form.