The indigenous have been resisting their possible eviction for months, operating with little or no information from authorities about what to expect, or what alternatives are available to them, said their leader Carlos Tukano.
"I know they are going to come in, and our proposal is to remain firm, but without moral or physical aggression," he said. "We cannot fight them with bows and arrows; they are armed."
Most of the approximately 30 Indians who live there and about 200 sympathizers packaged the compound Saturday to discuss how to peacefully deal with a possible police action. Several men, masking their faces with shirts, climbed high into the upper floors of the tumble-down building and surveyed the scene with professional bows and arrows.
The squatters believe they have history and the law on their side.
The crumbling mansion with soaring ceilings that housed the old museum was donated by a wealthy Brazilian to the government in 1847 to serve as a center for the study of indigenous traditions.
After the museum closed more than three decades ago, Indians of various ethnicities started using it as a safe place to stay when they came to Rio to pursue an education, sell trinkets in the streets or get medical treatment.
"They would come here without money, without knowing anyone, and sleep in the streets," Tukano explained. He himself is from a village deep in the Amazon. "We made this our space."
The head of Rio state legislature's Human Rights Commission, representative Marcelo Freixo, called for the need to stay calm and avoid violence.
"Conflict here is not in anyone's interest," he said before addressing the squatters and supporters inside the compound. "If there is a judicial order, the police will have to enforce it, but we have avoid any injuries with dialogue."
As he spoke, state public defender Eduardo Newton proposed an alternative legal tactic.
Under state law, Newton said, there can't be a mass eviction without proper legal proceedings. With group approval, he began gathering documents that would prove that more than 10 families lived on the grounds so he could try for a rushed stay on the eviction notice.
Police, meanwhile, police continued to stand guard the compound.