Strictly speaking it was never 'invented' but its principles were rediscovered as a means to attaining enlightenment and selfless expansion.
The various techniques sometimes regarded as Meditation were designed by various sages to help others reach the God Spark within.
These various techniques are necessary outward expressions of deeper truths for those lacking the clarity of Cosmic Consciousness. In Nirvikalpa Samadhi one goes beyond the outward forms of ritual out of neccessity, and inwardly percieves the divine truth itself.
For those specific practices which developed throughout the ages by various sages and yogis I will leave that for others to clarify as this could take quite some time!