In the English nursery rhyme and tongue-twister, how many pickled peppers did Peter Piper pick?

"Peter Piper" is an English-language nursery rhyme and well-known alliteration tongue-twister. It has a Roud Folk Song Index number of 19745.

The common modern versions:

• Peter Piper picked a peck of pickled peppers.
  
• A peck of pickled peppers Peter Piper picked.
  
• If Peter Piper picked a peck of pickled peppers,
  
• Where's the peck of pickled peppers that Peter Piper picked?

The earliest version of this tongue twister was published in Peter Piper's Practical Principles of Plain and Perfect Pronunciation by John Harris (1756–1846) in London in 1813, which includes one name tongue-twister for each letter of the alphabet in the same style. However, the rhyme was apparently known at least a generation earlier. Some authors have identified the subject of the rhyme as Pierre Poivre, an eighteenth‑century French horticulturalist and government administrator of Mauritius, who once investigated the Seychelles' potential for spice cultivation.