Spheres Eggs & Hearts
These shapes are both excellent for centering meditations.
If a circle is the perfect shape, a sphere is the perfect volume. Stars, planets and seeds. The thing I love about spheres is that unlike any other shape there's no sense of direction. It's not "pointing" anywhere . . . but inwards. I believe this is the reason for the famous use of crystal balls by seers. The clear quartz stimulates your consciousness, encouraging visual thought which in itself transcends the limitations of the logical mind, while the Sphere shape itself centres you which helps you not get carried away.
An Egg, viewed from the base, looks like a sphere. But it's beginning to attain direction and form - a new idea is being gestated and born.
Writing this I'm seeing a heart somehow as 2 eggs combining with a Sphere. What a symbol.