What are the devices and techniques that can be found in Keats's "On Visiting the Tomb of Burns"?

The first device we can talk about in this poem is its structure and rhyme pattern. "On Visiting the Tomb of Burns" is a sonnet in iambic pentameter, with the rhyme scheme abbaabba cdedec. It is a Petrarchan sonnet in form, as it uses enclosed rhyme for the octave and closes with a sestet instead of a rhyming couplet.
The next device we can talk about in this poem is its intertextual references: there are two that I will focus on.
The first is that the entire poem is a reflection on the Scottish poet Robert Burns. Keats is reflecting on a visit to this poet's tomb and the setting and events of his visit. By alluding to Robert Burns—considered to be Scotland's greatest poets, especially by the romantic poets among whom Keats was posthumously counted—Keats brings to the reader's mind all of the emotion and importance of that poet.
The second intertextual reference that Keats makes is to Minos, a character in Greek mythology who, among other things, became the judge of the dead in the underworld. In the sestet Keats asks if anybody has the "mind" to see the reality of "Beauty" like Minos did and exclaims in response: "Burns!" meaning that Burns' poetry has an almost mythological capacity to know and "relish" the truth just as Minos did.