Definition of "buttonlike"

[…] I was then, but slowly, drawn towards the closing vortex. When I reached it, it had subsided to a creamy pool. Round and round, then, and ever contracting towards the button-like black bubble at the axis of that slowly wheeling circle, like another Ixion I did revolve.

1851 November 14, Herman Melville, “-Epliogue”, in Moby-Dick; or, The Whale, 1st American edition, New York, N.Y.: Harper & Brothers; London: Richard Bentley

[He] was smoking slowly and calmly, and looking at nothing at all with his black buttonlike eyes.

1922, E. E. Cummings, chapter 7, in The Enormous Room‎, New York: Boni and Liveright, page 153