In the recent past people have generally believed that the arthashAstra represents one of the earliest mentions of dhattUra (Datura metel) that is believed to be of pre-Columbian New World origin. Is the mention of the dhattUra in the AS for true? It supposedly comes in the section on liquors and is believed to be mentioned in 2.25.33 along with a whole range of other plants. These plants are supposed to be additives to produce flavored drinks. The manuscripts used by Kangle in his edition of the AS have the word pattUra and not dhattUra. One of his manuscripts termed G1 has it as vattUra. Kangle notes that G1 was copied from a source in the malayALaM script in which ‘va’ and ‘pa’ are close and can be conflated (also seen in Tamil grantha e.g. avamAnaM for apamAnaM). Hence, in all likelihood it was pattUra and not dhattUra. The general belief is that pattUra is a distinct plant, namely Achyranthes triandra or Alternanthera or generically some member of Amaranthaceae. So it is unlikely that the toxic Datura was being added into the liquor of the arthashAstra.
Likewise, I have not seen any evidence for the mention of this plant in the two itihAsas or charaka, the earliest of the 3 great medical saMhitA-s of the Hindus. While the domain of artha is apparently lacking in unmatta, the kAmasUtra of vAtsyAyana does seem to have it. It is mentioned in 7.1.25 as a component of a concoction that is applied on the li~Nga (dhattUraka-marica-pippalI-cUrNair madhu-mishrair lipta-li~Ngasya samprayogo vashI-karaNam). If there is any reality to this claim it might be the supposed erogenic role of tropanes. Likewise, both dhattUra and pattUra are apparently mentioned in the medical saMhitA of sushruta. Thus, the kAmasUtra and the sushruta saMhitA happen to be the earliest surviving texts with a mention of the dhattUra plant in the old world. The absence of evidence is not necessarily evidence for absence. However, it should be noted that the number of references to dhattUra in the texts that temporally post-date these two texts only increases. In the Astika and nAstika tantric literature (as noted in the latter by the Eastern European scholar Siklos) the plant is very prominent along with much older plants that are already found in the atharvan literature (e.g. apAmArga). This might give us a means of fixing temporal window of the introduction of dhattura to India. Of course this later introduction would leave one uncertain about the psychoactive substance used by the vedic muni psychonauts. In the RV (10.136) the muni-s are mentioned as using a viSha (also possibly AV-paippalAda 5.17.3 where the word unmatta is used in connection with the muni), but in light of the above there are serious doubts if it is dhattUra as otherwise assumed.