The Secret Of The Golden Flower
Osho suggests that the best time to do this meditation is just on waking in the morning, before getting out of bed and just before falling asleep in the evening. He describes the meditation as follows:
Simply lie down , as you are lying down in your bed, on your back. Keep your eyes closed. When you breathe in, just visualize great light entering from your head into your body, as if a sun has just risen close to your head – golden light pouring into your head. You are just hollow and the golden light is pouring into your head, and going, going, going, deep, deep, and going out through your toes. And when you breathe out, visualize another thing: darkness entering through your toes, a great dark river enterin through your toes, coming up, and going out through the head. Do slow, deep breathing, so you can visualize. Go very slowly. Let me repeat: Breathing in, let golden light come into you through your head, because it is there that the golden light is waiting. The golden light will help. It will cleanse your whole body and will make it absolutely full of creativity. This is male energy. Then when you exhale, let darkness, the darkest you can conceive, like a dark night, riverlike, come from your toes upwards – this is feminine energy, it will sooth you, it will make you receptive, it will calm you, it will give you rest – and let it go out of the head. Then inhale again, and golden light enters in. Do it for twenty minutes early in the morning. And the second best time is when you are going back to sleep, in the night. Lie down on the bed, relax for a few minutes. When you start feeling that now you are wavering between sleep and waking, just in that middle, start the process again and continue for twenty minutes. If you fall asleep doing it, it is best, because the impact will remain in the subconscious and will go on working. And after a three month period you will be surprised: the energy that was constantly gathering at the muladhar, at the lowest, the sex center, is no longer gathering there. It is going upwards.
(Osho in The Secret of Secrets, volume 2