Morton's Letheon: When was the name Letheon chosen?

Letheon was the commercial name that Boston dentist William T. G. Morton chose for his ether-based "preparation" that was inhaled to produce insensibility during surgical and dental procedures. The multiple editions of Edward Warren's Some Account of the Letheon (1847) as well as Nathan P. Rice's Trials of a Public Benefactor (1859) provide the only known accounts of the meeting hosted by the physician Augustus A. Gould at which the name Letheon was chosen. Neither Warren nor Rice mentions when the meeting occurred. In all likelihood, it was held at some point in a three-week period from mid-November to just short of December 9, 1846, the publication date of the earliest known reference to the name. The absence of the word Letheon in Morton's public notices around the end of November 1846 or, indeed, in any document until his December 9 advertisement in The Boston Medical and Surgical Journal suggests a later date for the meeting than has been previously reported.