The Indian tractates are set of short ancient Greek writings about India associated with Alexander the Great. They are not authentic in terms of their supposed authors and addressees, but rather are part of the extensive legends about Alexander.
The four tractates are:
All four were interpolated at some point into the Latin text of the Alexander Romance. The earliest manuscript with a version of the Romance including all of the Indian tractates is in Bamberg, Staatsbibliothek, Msc.Hist.3 (olim E.III.14) of the 10th century. Unconnected with Alexander but also fictitious is the Letter of Pharasmanes to Hadrian, which describes the marvels of the East. It was also used as a basis for augmenting the Romance.