The word Khorasan finds mention in many ancient texts pointing to a place in Middle east to Afghanistan . The question is what were the boundaries of the historical Khorasan which parts of the middle east were included in Khorasan.
Wiki says that Greater Khorasan, a historic region which lies mainly in modern-day Iran. It was previously known as Parthia; later, during the Sassanid era, it was renamed to Khorasan. But the etymological meaning of Khorasan (Persian) is "land of rising sun".
Thus wanted to know which regions of earth were included in Khorasan of 1500 years ago?