The text of a revelation by Joseph Smith about selling the copyright of the Book of Mormon has been kept from the public until the publishing of the Joseph Smith Papers Project volume “Revelations and Translations.” There, on page 31, the revelation is in full just as David said: Joseph did try to sell the copyright of the Book of Mormon in Canada.
Wherefore be dilligent in Securing the Copy right of my Servent work upon all the face of the Earth of which is known by you unto unto my Servent Joseph & unto him whom he willeth accordinng as I shall command him that the faithful & the righteous may retain the temperal Blessing as well as the Spirit[u]al & also that my work be not destroyed by the workers of iniquity to their own distruction & damnation when they are fully ripe & now Behold I say unto you that I have covenanted & it Pleaseth me that Oliver Cowderey Joseph Knight Hyram Page & Josiah Stowel shall do my work in this thing yea even in securing the ∧Copy∧ right & they shall do it with an eye single to my Glory… (“23 Commandment AD 1830,” Revelation Book 1, The Joseph Smith Papers, p.31, https://www.josephsmithpapers.org/paper-summary/revelation-book-1/15
Disparagers of David have tried to mar his reliability by pointing to the fact that David said they went to “Toronto” not “Kingston” Canada. The truth is, his brother kept the Revelation Book and thus David knew exactly what the revelation said. By citing “Toronto” (where buyers could be found) David tried to minimize the damage to Joseph, so the error was one of circumventing Martin Harris and not of getting the city wrong also (see False Revelations for further light).