The story of an Iliad written in characters so small that it could be packed in a nutshell is given by Pliny, Natur. Hist. Book III, ch. 21,
'In nuce inclusam Iliada Homeri carmen in membrana scriptum tradit Cicero.'
The allusion is not found in any of the extant works of Cicero. The elder Scaliger refers to the passage in Pliny in his book De Subtilitate, which Swift seems to have read. Cf. p. 189, 1. 31 (note).