The Mugnone River is the setting for Calandrino’s search for a supposed invisibility stone, a trick that turns the riverbed’s commonplace stones into props and lets the joke follow him back toward Florence. Its narrative importance lies in the contrast between the ordinary place and the extraordinary power Calandrino believes it contains.

Setting and Access

The river is presented through its bed and the route along it rather than through a description of its wider landscape. Calandrino and his companions leave Florence through the San Gallo Gate and descend into the Mugnone’s bed, searching downstream. Their return follows the stream back to the same gate, making the riverbank part of a path between the city and the prank’s staged conclusion.

The Search for the Heliotrope

Maso tells Calandrino that a stone called heliotrope can make its bearer invisible, and claims it is commonly found in the Mugnone. He describes the stones as nearly black and advises searching on a Sunday morning, when fewer people will be about. Calandrino believes him, recruits Bruno and Buffalmacco, and keeps the supposed discovery secret from everyone else.

On Sunday, Calandrino eagerly gathers every black stone he sees. He fills his bosom, gathers up his gown to make a larger carrying pouch, and then loads stones into his mantle as well. The river supplies no magical object: the search’s abundance of ordinary stones lets the deception appear, to Calandrino, to be succeeding simply because he has collected so many.

The River as a Stage for the Prank

Once Calandrino is heavily burdened, Bruno and Buffalmacco pretend they can no longer see him. Their feigned confusion makes him think he has found the heliotrope and become invisible, even as he walks beside them. They then strike him with stones, first on the shins and then in the small of the back. Calandrino feels the blows but stays silent, interpreting the attacks through his belief that his companions cannot see him.

The trick continues as the group travels up the Mugnone toward the San Gallo Gate. There, Bruno and Buffalmacco put down the stones they have gathered and pause at the customs house. The officers, forewarned by the pranksters, also pretend not to see Calandrino and let him pass. The deception thus expands from the river search into a coordinated performance involving people at the city entrance.

Narrative Significance

The Mugnone’s role depends on the gap between the river’s ordinary material reality and Calandrino’s credulous reading of it. Its black stones seem to offer proof of the magical claim, while the river route gives Bruno and Buffalmacco room to stage the supposed disappearance and extend the joke toward town. The illusion ends when Calandrino reaches home and his wife, Mistress Tessa, sees him; her recognition exposes the limits of the invisibility he believed the river had given him.