Ancient POIMaori Poi were made from flax blades, raupo, corn husks and core pith. Maori men used rocks (helping to build those muscles). Shape of Poi originally didn't matter. It could be ball or egg shaped. Cord length came as 82cm (long poi), 30cm (three-quarter), 25cm (short poi). Even now the shape does not matter.
POI todayThese still consist of the Poi head, cord and grip/handles.
Modern Maori Poi consists of paper, foam, plastic, wool and strings.
Poi has also developed into FIRE POI, Tailed/Ribbon Poi and Lighted Poi. Materials used for these are aluminum, wood, stainless steel, brass, nylon, ripstop nylon, hi-impact plastics, hi-tech man made fibers, KEVLAR ®, cotton, fluorescent chemicals and electronic circuitry.Weight is very important. A lighter Poi suits a short cord and heavier Poi suit a longer cord. This weight is necessary to overcome gravity on the upward swing. A light Poi on a long cord may not swing properly at the top of its flight. Also if you are performing outside a light Poi will we blown about and made very hard to control. A very heavy Poi may be good in the wind, but it could damage and strain your muscles, or even worse break the cord/chain and fly off and hit your audience.
See also Which material should I use for wick?, What is KEVLAR ®?, Guide to selecting metals for fire equipment, Your guide to ball chain cords and components.