take, cherish, sheaf, unit of volume (10 koku; 1,800 l)
秉 centers on holding something firmly and carefully: taking something in hand, cherishing or keeping it, and by extension a bundled sheaf of grain or a historical unit of volume.
秉 combines 禾 (grain plant) with a hand shape 彐, depicting a hand holding a sheaf of grain. The modern form preserves this image of grasping or cherishing.
The top is a grain plant 禾, and the lower part looks like a hand holding it. Picture a hand carefully grasping a sheaf of grain: that is taking, cherishing, and a bundled unit.
For ヘイ, imagine a hand holding a sheaf of hay: hay -> ヘイ, and the hand cherishes the bundled grain.