Tomes of Clear Thought are magically tomes that increase the primary ability of Intelligence by one point and are consumed when the point is added. This item appears in Baldur's Gate and Baldur's Gate: Enhanced Edition.
In BG, it can be found at the top of Ramazith's Tower, in a library.
|“||A typical tome of clear thought contains a collection of esoteric and scholarly literature, often involving obscure mathematical or algebraic formulae or the occasional reference to inter-planar biology. Such tomes are usually magically enhanced, thereby allowing an individual to raise his or her Intelligence by a single point. Unfortunately, the manual will disappear after a single use.||”|