a child picking up shells

I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.

Samuel Johnson alludes to this comment in Rambler 83:

To mean understandings, it is sufficient honour to be numbered amongst the lowest labourers of learning; but different abilities must find different tasks. To hew stone, would have been unworthy of Palladio; and to have rambled in search of shells and flowers, had but ill-suited with the capacity of Newton.