The two handled bowls/drinking cup the oath takers drink of is called a quaich. The word is Scottish Gaelic and means "cup".
The instructions that Claire gives Laoghaire for the "love potion" are actually a modified version of how Dorothy from the Wizard of Oz is told to get back home. Ie tap your heels together and say there's no place like home/love.
While the camera first pans over the gathering in the great hall (15:28), Outlander show runner Ronald D. Moore can be seen briefly in the middle of a group of dignitaries, posing as a Scottish lord.
At the Gathering, you can clearly see Iona Claire (who later appears as Fiona in the 1960s) as an extra.
Diana Gabaldon: The author of the Outlander series has an appearance as Iona MacTavish, a wealthy merchant's wife who exchanges words with Mrs. Fitz on the balcony in the hall.