According to Official Guinness Records,
The greatest altitude at which a formal meal has been held is 6,805 m (22,326 ft) by Henry Shelford, Thomas Shelford, Nakul Misra Pathak, Robert Aitken, Robert Sully (all UK), Caio Buzzolini (Australia) and appointed butler Joshua Heming (UK), who dined on Lhakpa Ri, Tibet on 3 May 2004.
The expedition team named “Henry Shelford’s 30th birthday party” were set to dine on the summit of the 7,054 m (23,113 ft) mountain but hurricanes forced them to descend to a more sheltered spot.
The team carried the tables, chairs and silver cutlery as part of the expedition and dined on a feast of caviar as a starter, duck for main course, chocolate bombe for dessert, cheese and wine, followed by birthday cake to finish.
For a complete list of 2004 records, please visit 2004 Guinness Records in China.