To quote from the linked article and a question:

http://www.spaceref.com/news/viewpr.html?pid=18675

"Other spacecraft like Pioneer 10 and 11 and Voyager 1 and 2, have flown further than Pluto but never ventured near it. They carried politically correct "greetings from Earth" on plaques and phonograph records. But not New Horizons.

"The mission's lead manager Alan Stern from the Southwest Research Institute at Boulder, Colorado, told AW&ST that doing something like that involved too much federal bureaucracy.

"Instead, the half-ton New Horizons spacecraft is carrying the names of more than 430,000 space enthusiasts and a piece of material from Burt Rutan's SpaceShipOne, the first privately built manned spacecraft. It is also carrying material commemorating Pluto's discoverer Clyde Tombaugh, who was cremated after his death in 1997 at age 90."

What are the "material commemorating... Clyde Tombaugh" aboard New Horizons?