Interesting that it doesn't seem to have been stopped for security concerns or whatever.
quoth the BBC:
The artists posted the parcel at a post office in east London on Wednesday at 12:43 GMT. Later, they emailed Mr Assange to explain the project.
"The parcel is a live mail art piece. It is intended as REAL_WORLD_PING, a SYSTEM_TEST inserted into a highly tense diplomatic crisis," the email read, making reference to program code functions.
"Since you took refuge there in June last year, the Ecuadorean embassy in London has been the spectacular staging of an intense clash between the international order and freedom of information activists.
"We want to see where the parcel will end. Which route it takes and whether it reaches you."