Occupy Central won't just be about relieving protesters' desire for democracy; organisers say they also have to worry about the 10,000 participants relieving themselves.
Food, water and - most of all - toilets were occupying the minds of the organisers, founder Benny Tai Yiu-ting said yesterday, the first time he has discussed the practical issues Occupy faces.
And Tai was careful not to leak further details for fear of being charged with conspiracy or incitement to break the law.
"There are big and small things we need to consider," Tai said, ahead of a crunch meeting of the Standing Committee of the National People's Congress on political reform in Hong Kong.
Tai and others have hinted that the committee's decision could trigger Occupy's plan to rally 10,000 people to block streets in the business hub.
"The big thing is which part of Central should be occupied so that the biggest possible crowd can gather," he told RTHK. "The small thing is people won't have food and water.
"They may be able to bear this for a period of time, but when it comes to toilets, they may just leave if they can't go to the loo."
Tai said the movement would need time to prepare, and would have to assess whether the public was sympathetic to its cause.
There are two public toilets near Chater Road, where a rehearsal for Occupy was led by students in July: one in the car park of the old Star Ferry Pier, and the other near Bank Street. Another seven are further away.
The NPC Standing Committee gathers tomorrow for talks on reform as the city discusses how to implement universal suffrage for the 2017 chief executive election. Its decision is expected to set Beijing's bottom line ahead of a second round of consultation by the Hong Kong government later this year.
At a forum yesterday, Tai said either of two rules the committee could set would prompt Occupy to take place. The first would be a requirement that candidates in 2017 win the support for more than half of the members of a nominating committee before being put to the public. The second would be a low limit on the number of candidates.
But fellow forum participant Lau Nai-keung, a member of the Basic Law Committee under the NPC Standing Committee, said Beijing was likely to limit candidate numbers; it would consider two or three a "safe" limit.
Meanwhile, the head of the Hong Kong government's Central Policy Unit said yesterday that it was reasonable to rule out any candidate who threatened national security - including that of the Communist Party.
"If the candidates go to the White House to meet someone and then go to London to meet someone, how can they gain the central government's trust?" said Shiu Sin-por, in a reference to recent attempts to win Western support by veteran democracy fighters Anson Chan Fang On-sang and Martin Lee Chu-ming.
But Shiu said Occupy would be acceptable as long as participants took responsibility for breaching the law and pleaded guilty to any criminal charges.
Additional reporting by Shirley Zhao