1. Autograph letter signed from George Thomson to Anne Power, née Horner, Leith (Edinburgh), 26 July 1850 : “The last time I ask’d a collector of rarities if he could give or sell me an autograph of Burns, his reply was, Why Sir you might as well ask me for that of Moses! I Iong ago parted with any scraps I had of the Poet, and have since been obliged to say No to an hundred applications at least; having got all his precious letters with his Songs splendidly bound, and I could not on any account allow myself to mutilate them, else one of the Horner family should not solicit me in vain. You have no idea of the eagerness of collectors to obtain his illustrious name of his own writing [...]”.

2. Autograph letter signed from George Thomson to Aeneas MacBean, Laurel Bank, Lasswade (near Edinburgh), 9 June 1846: “I return the second volume of Horner with my hearty thanks for the pleasure I have received from the Work, so honourable to the name and Country of Horner, who by the force of his talents his virtues and his most amiable temper & disposition, raised himself to the companionship and admiration of the first men of the State, and if his life had been prolonged, would in all probability have raised him to the rank, only exceeded by Royalty. It gives me pleasure to see Leonard occupying such a dignified position in London. Too much honour cannot be bestow’d on the brother and Relatives of the ever to be regretted Francis Horner. Leonard’s simple account of the last duties to his dear brother touch’d me most sensibly – I pictured him standing desolate forlorn overwhelmed with grief! and what his feelings must have been when he took his last look at the Cemetery! [...]”.