The best pose is the one in which you are comfortable. In Patanjali’s Yoga Sutras, he writes, “Posture should be that which is steady and comfortable.” Your pose should be steady enough that you can hold it easily for the duration of your meditation. However, what Patanjali points out is that only a comfortable pose can truly be steady, otherwise you will fidget and be distracted by your discomfort.
That being said, a cross-legged pose facilitates deeper meditation – if that cross-legged pose is comfortable for you. You can even sit on a chair and cross your legs at the ankles.
It is also best to sit upright, but not rigidly so. It is also fine to rest your back, but do not rest your head or you will fall asleep. Above all, remember that this is meditation and not gymnastics. The main purpose of the meditative pose is to allow you to forget the body and go inward