Membership to the NYSE.
Owning a seat on the NYSE enables one to trade on the floor of the exchange, as an agent either for someone else (floor broker) or for one’s own personal account (floor trader). The phrase "owning a seat on the exchange" originates in a time before 1871, until which the exchange operated in a 'call-market' fashion, which means stocks were traded individually. With this type of trading, each member would sit in an assigned seat and participate in the buying and selling of desired stocks as they were called for trading.