What is the relationship between the Buddhist meaning of emptiness and the Daoist meaning? Are they inherently the same? Do both of the teachings have a concept of the dao?
In Taoism the Emptiness creates 1 which then creates 2 and 3 which then creates the whole universe, as referred to in the previous response: Emptiness as the "mother of the Ten Thousand Things." This is from the Tao Te Ching.
In fact that teaching is from music theory and so to say Emptiness equals form in Taoism has the specific meaning of the Tai Chi as the form of 1:2:3:4 which is also the Pythagorean Tetrad from music theory - the Octave, Perfect Fifth and Perfect Fourth.
The secret of the Emptiness is then the secret of "one hand clapping" as the Ch'an Koan is called - or what in Buddhism is called the "inner sound method." This secret form is then based on the complementary opposites of the Tai Chi. You can study the alchemy books Taoist Yoga: Alchemy and Immortality for details and also the Hui Ming Ching, the source book for the first one. Also Wang Mu's Foundation of Internal Alchemy.
The teacher I studied with - a Shaolin trained alchemist qigong master teaches "the simplest is the most powerful" and how the 1 from the Tao te ching is the consciousness that goes into the Emptiness (the Wu Chi) which then creates the yin/yang 2:3 energy of the Tai Chi. The consciousness is our spirit light as visualization.
The Taoist Yoga: Alchemy and Immortality book states very clearly that only the "absolute void" enables a person to see light outside their body - the light "radiates" whereas the internal light that we see with our eyes closed is not the real Emptiness, rather it is limited to the body qi or "yin qi" or psychic lunar energy.
So going back to music theory the form 1:2:3:4 that is the emptiness means that yin and yang change their value based on the order of resonance as a spacetime vortex (the emptiness). In music theory frequency is 1:2 and 2:3 and 3:4 as subharmonics and then time is the inversion. So we learn music theory as a wavelength but what is covered up is that the geometry of space is noncommutative or "complementary opposites."
Buddhism is based on Vedic logic which is a phonetic based language of dualistic symmetric math that still covers up this Taoist and Pythagorean secret of complementary opposites. The "three gunas" of India - the oldest philosophy of India - tamas, raja, and sattva, also originate from the music complementary opposites of the octave, perfect fifth and perfect fourth. So this older music theory truth of yoga training in India is from the "three gunas." All human cultures use this octave, perfect fifth and perfect fourth natural harmonics as the basis of spiritual trance harmonics - even babies cry in these simple number frequencies as being most consonant.
So in the West based out of Vedic logic this secret was covered up by the simple fact that 2 as a number does not go into 3 and so the Perfect Fifth harmonic ratio does not go into the octave. Anyone learning basic music theory learns that the Perfect Fifth plus the Perfect fourth equals the octave but this is a lie that covers up the Tai Chi form as the Emptiness! Why is it a lie? Because in order to "add" the Perfect Fifth and Perfect Fourth you actually "multiply" as a logarithm assuming a commutative or symmetric mathematical logic! This means to subtract the Perfect Fourth (yin) from the Perfect Fifth (yang) you then divide and the result is 9/8. This can only work by using the harmonics over the 1 value - ignoring the subharmonics of 2/3 and 3/4.
So let's convert the yin and yang to geometry - 2/3 as subharmonic is C to F or yin and 3/2 as harmonic is C to G as yang. Both are a perfect fifth energy! In fact this is the secret of alchemy - to resonate your yin energy as a complementary opposite into yang energy! But again this empirical truth is covered up by the dualistic symmetric logic of the West starting out of Brahmin Vedic logic. So then 2/3 is not allowed because it can not be converted into commutative symmetric logic and so 2/3 as yin is "doubled" to 4/3 so that it is no longer a Perfect Fifth subharmonic and instead is a Perfect Fourth overtone harmonic.
Do you see what just happened here? The "one" value that creates the octave was changed! The "one" was changed to the "two" doubled to 4 as the numerator. So with the harmonic series you can not use 4/3 as an overtone harmonic since 3 is the denominator and 3 is not an octave "same note" multiple of the one. You can have 2/1 as the octave of one or 1/2 and 3/2 as the yang Perfect Fifth but not 4/3. So this is called the "phantom tonic" in Western music theory - the Perfect Fourth can not be "created" from the One - why? Because the whole point of Western music theory, which is the foundation of Western symmetric logic, is to "contain" the Emptiness into a material geometry.
So then what happens when we change the "one" to the means of doubling the subharmonic as the new "phantom tonic" so that the 2 is now the numerator as 4/3? Again we get the Perfect Fifth as 3/2 x the Perfect Fourth as 4/3 = the Octave as 2/1. This would appear to be a balanced harmony of yin and yang and Emptiness - but again this covers up the real mystery of the Emptiness and instead converts it into a commutative or symmetric logic. So as I stated the difference between them is 9/8 by dividing them as a logarithm and so 9/8 is the major 2nd interval or "whole step" of the scale - the goal of this scale is to "compromise" the empirical truth of the infinite Yang as 3/2 - the infinite spiral of fifths. So then 9/8 as six whole tones has a value which is slightly over the value of the octave! They do not line up! 9/8 cubed then approximates the square root of two. This is the secret cover up of the truth of how form is Emptiness. The Emptiness is turned into a "divide and average" symmetric logic that is from Vedic Brahmin cipher symmetric geometry logic.
O.K. so what do we have if we remain true to the empirical reality of the "infinite spiral of fifths" or the "true yang" secret of alchemy? As I stated the subharmonic is 2/3 as yin or C to F geometry and the overtone harmonic is 3/2 as yang or the Perfect Fifth C to G. It's the same C as the root tonic - no need to "change" the tonic by doubling 2/3 to 4/3. Instead we embrace the fact that with the same C as the 1 we have different geometric values based on the direction of the spacetime. This is called noncommutative geometry - or asymmetric complementary opposites of the Tai Chi. This is the real secret of music theory - the perfect fifth can never be the same value divided equally into the octave and yet they harmonically resonate as complementary opposites infinitely as the Emptiness. There is no commutative logarithmic value to infinity as a materialistic containment or Perfect Fifth plus Perfect Fourth equals Octave based on wavelength. There is instead a harmony based on time-frequency energy. Everything is energy - even in the Emptiness. This is called the "yuan qi" as the formless source of the Universe.
the primal qi” (li yuanqi 理元氣), since they are themselves formless.
This secret was rediscovered by Louis de Broglie in quantum physics where energy is also based on time-frequency inverse proportions from Pythagorean philosophy, the foundation of Western science. What de Broglie discovered is that for Einstein as matter goes towards the speed of light then the frequency energy increases but also the time as wavelength increases and this violates the Law of Pythagoras - the original complementary opposites of time and frequency. So de Broglie discovered that frequency is to time as momentum (mass x velocity) is to wavelength. This also meant that there has to be a "pilot wave" that comes from the future and so is "faster than light" or superluminal and it harmonizes in phase with the matter going slower than the speed of light. This is called the Law of Phase Harmony by Louis de Broglie and it is being confirmed now that in fact quantum entanglement is the foundation of 3D spacetime.
https://books.google.com/books?isbn=1107093503Chenyang Li, Franklin Perkins - 2015 - PhilosophyLater Daoists used the term “primordial qi” (yuanqi 元氣) to designate the state ... space and formless qi that preceded the existence of the ordered cosmos.
So this explains how precognition happens by doing the Taoist alchemy training based on the secret of the Tai Chi form equaling the Emptiness and also how when the energy is strongest as light frequency then the time is the shortest.
Again for the actual practice as per the body-mind meridians you need to study the Taoist alchemy texts I referred to which also are inspired by the Emptiness of Buddhism as well. But the thing is that Buddhism was a reform to Brahmin religion and so as Buddhism spread into China it adapted to Taoism and hence the syncretic overlap. As I've stated there is an older tradition of India of the "three gunas" that is also based on the actual music empirical truth of complementary opposites as the Tai Chi.
For those looking for me - this is from "drew hempel"