"No. No!" Miss Imogen smiles as she looks along the arrow shaft and suddenly sees that she should have noticed before. "Slots. Slots for coins." She lowers her bow and points. "It's another puzzle."
She drops her pack, and fishes inside for her coin purse. She's not needed it for months now, it seems. And she reaches in, deep within, and pulls out a small leather purse that has been stiffend into an ungainly shape through repeated soakings, as she had made her way through the jungle. She works to pull it open, and inside... are 19 tarnished gold coins. Only gold. She removes one of them, and walks to the pillar that had gold on the top.
"Is this an offering? Or something that activates?" she asks aloud, but to herself. Then to the others: "Does it matter which we do first? Does anyone have a copper piece? We could start with that one. See what happens."
If anyone has copper, she's content to let them use that slot. Otherwise, she'll do gold. Her pack's on the ground but the bow is still in her hand, quiver at her hip.