I found an amazing activity from the book, Crystals for Witches by Eliza Maybelle.
Connecting to the Astral Realm
What you need:
1 brown jasper (or any brown, earthy crystal)
1 selenite stone (she says oval but any will do)
What to do:
Sit in a quiet place to meditate. Place the jasper in your right hand and the selenite in your left.
Feel the physical differences in the stones; notice each one’s weight, temperature and texture. Notice their distinct vibrations. Jasper is earthy and stable, whereas selenite has an etheral feel to it.
Visualize the jasper growing roots like a tree, spreading into your hand, through your Armand down your body into the ground. The jasper stone roots you into the physical plane.
Visualize the selenite emitting a glowing white light that flows into your hand, up your arm, and bursts out of the crown of your head. This light reaches so far into the sky you cannot see where it ends; the astral Realm is infinite.
Focus on the roots below you and the light above you. Notice how energy of the two stones merge inside your body, separate but together. Your physical body is of the earth, like the jasper. Your spiritual self is of the astral, like the selenite. Together they create a perfect balance.
Allow this energy to flow you for as long as you are comfortable. Enjoy the feeling. You may become aware of sounds, images, or other sensations. These are the two realms communicating with you.
When you’re finished, write down any thoughts or images that came to you during this experience. They may not make sense right now, but the more often you practice this meditation, the more meaningful the information will become.
This meditation aligns your spirit body with your physical body, which creates a sense of purpose and harmony. It should feel extremely relaxing, and you should feel balanced and content afterwards.