| RefNo | Title | Date |
| MM/3/37 | Letter from W H Craft, Holborn, to Joseph Planta | 4 December 1792 |
| IM/003595 | Planta, Joseph | nd |
| MM/3/38 | Letter from Archibald Alison, Kenley, to Joseph Planta | 1 December 1792 |
| IM/003596 | Planta, Joseph | nd |
| RSL/2/2 | Letter from JK, Cork, to Joseph Planta | 4 February 1786 |
| MM/3/60 | Letter from William Drysdale, Newcastle, to Joseph Planta, Secretary, Royal Society | July 1798 |
| MM/4/31 | Letter from Robert Crew, Secretary, Board of Ordnance, to Joseph Planta, Secretary, Royal Society | 29 May 1801 |
| MM/4/34 | Letter from Col William Congreve, Charlton, to Joseph Planta, Secretary, Royal Society | 29 June 1801 |
| MM/4/35 | Letter from Robert Crew, Secretary, Board of Ordnance, to Joseph Planta, Secretary, Royal Society | 25 February 1803 |
| MM/4/33 | Draft of a letter from Joseph Planta, Secretary, Royal Society, to Robert Crew, Secretary, Board of Ordnance | 11 June 1801 |
| MM/3/64 | Letter from Capt William Mudge, Royal Artillery, to Joseph Planta, Secretary, Royal Society | 6 February 1799 |
| CB/1/3/95 | Letter from R H Crew, Office of Ordnance to Joseph Planta | 10 June 1790 |
| CB/2/575 | Copy of a letter from Charles Blagden to Joseph Planta | 9 October 1791 |
| CB/2/310 | Copy of a letter from Charles Blagden to Joseph Planta | 15 September 1789 |
| CB/1/5/224 | Letter from J Planta, Foreign Office to Charles Blagden | 11 September 1817 |
| L&P/8/141 | Letter, 'Observations on the late comet' from J D Pearse to Joseph Planta | 8 April 1784 |
| L&P/6/205 | Letter, 'Essay towards discovering the degree of cold' from Joseph Mead to Joseph Planta | 1 September 1774 |
| L&P/6/141 | Letter, 'An account of the Romansh language' from Joseph Planta to John Pringle | 1775 |
| L&P/7/123 | Letter, 'On Thomas Everitt, the big boy' by Richard Gough to Joseph Planta | 25 November 1779 |
| L&P/6/242 | Letters, 'On various subjects' from Charles Bacheley to Joseph Planta | 3 April 1777 |
| L&P/9/7 | Letter, 'Conjectures on some of the phenomena of the barometer' from Robert McCausland to Joseph Planta | 6 April 1786 |
| L&P/7/26/1 | Papers, 'An accident by lightning at Purfleet' by Edward Nickson, Benjamin Wilson, William Henly, Edward Nairne, Timothy Lane, John Boddington and Joseph Planta | 19 June 1777 |
| MM/3/56 | Letter from J Skinner and Edmund Benson, Sarum, to Joseph Planta, Secretary of the Royal Society | 25 March 1797 |
| MM/3/63 | Letter from RM Crewe, London, to Joseph Planta, Secretary, Royal Society | 8 February 1799 |
| MM/3/57 | Copy of letter from Joseph Planta, Secretary, Royal Society, to J Skinner and Edmund Benson | 8 April 1797 |
| EC/1773/32 | Planta, Joseph: certificate of election to the Royal Society | |
| AP/5/25 | Unpublished letters and paper, regarding the ramming of fuses for bombs by John Macdonald | 1786-1787 |
| AP/5/25/1 | Unpublished letter, regarding Macdonald's paper on bombs from Will [William] Roy to [Joseph] Planta | 20 December 1786 |
| AP/5/24/2 | Unpublished letter, regarding paper on convulsive illness from Raymond to unknown recipient | 12 April 1785 |
| L&P/6/257 | Paper, 'Report on the graduation of thermometers' by the Royal Society Commitee | 1777 |
| L&P/7/26 | Papers, 'An accident by lightning at Purfleet' by Edward Nickson, Benjamin Wilson, William Henly, Edward Nairne, Timothy Lane, John Boddington and Joseph Planta | 19 June 1777 |
| AP/4/5 | Unpublished paper, 'Further observations, relative to some experiments, on the nerves of living animals' by Wm [William] Cruikshank | 28 November 1776 |
| L&P/10/81 | Paper, 'Observations on some Egyptian mummies opened in London' by Johann Friedrich Blumenbach | 15 December 1793 |
| HS/14/166 | Letter, from Joseph Planta to Sir John Herschel, dated at Hampstead | undated |
| L&P/10/60 | Letter, 'Concerning the discovery of a comet' from Caroline Herschel to Joseph Planta | 8 October 1793 |