Full Idea
Over and above what can be deduced from extension, we must add and recognise in bodies certain notions or forms that are immaterial, so to speak, or independent of extension, which you can call powers [potentia], by which speed is adjusted to magnitude.
Gist of Idea
As well as extension, bodies contain powers
Source
Gottfried Leibniz (De Natura Corporis [1678], A6.4.1980), quoted by Daniel Garber - Leibniz:Body,Substance,Monad 3
Book Reference
Garber,Daniel: 'Leibniz: Body, Substance, Monad' [OUP 2009], p.117
A Reaction
He boldly asserts that the powers are 'immaterial', but is then forced to qualify it (as he often does) with 'so to speak'. The notion that bodies just have extension (occupy space) comes from Descartes, and is firmly opposed by Leibniz.