The report states that Thackeray "found unquestionable evidence for the smoking of coca leaves in early 17th century England, based on chemical evidence from two pipes in the Stratford-upon-Avon area. Neither of the pipes came from the garden of Shakespeare. Four of the pipes with Cannabis came from Shakespeare's garden."
On loan from the Shakespeare Birthplace Trust in Stratford-upon-Avon, the pipes were tested for chemical residues (using the non-invasive technique of gas chromatography mass spectrometry). Several of the pipes had come from The Bard's garden. In his letter published in the South African Journal of Science, Thackeray also claims to have deciphered several of the bard's literary references to marijuana.
The journal states: "Thackeray (unpublished manuscript) suggests that Shakespeare preferred Cannabis as a stimulant which had mind-stimulating properties. These suggestions are based on the following literary indications. In Sonnet 76 Shakespeare writes about 'invention in a noted weed'. This can be interpreted to mean that Shakespeare was willing to use 'weed' (Cannabis as a kind of tobacco) for creative writing ('invention'). ... Sonnet 76 may relate to complex wordplay relating in part to drugs (compounds and 'weed') ..."