Manual of Gainful Exercise
Wondrous Item,
Very Rare
(cost 20000 gp)
Crafting Components
Dung beetle’s legs, essence from an Elemental Plane
This magical book outlines a vigorous exercise regimen. Spending 48 hours over 6 days (or fewer) reading and following the book’s regimen increases your Strength score and your maximum Strength score by 2. The manual then becomes a mundane item for a century before it regains its magic.
Source