Here he studied the Hebrew, Greek and Latin languages, and became familiar with the (banned) writings of Martin Luther and William Tyndale as well as the technology of printing.
Brinley Jones describes the remarkable range of Salesbury's writings, "the product of a Renaissance humanist scholar, lexicographer, and translator".
[3] In 1550 his A briefe and a playne introduction, teachyng how to pronounce the letters in the British tong (now commonly called Walsh)... was printed by Robert Crowley.
A revised edition was printed "by Henry Denham for Humphrey Toy, at the sygne of the Helmet in Paules church yarde, The.
In 1547 he published a collection of 930 Welsh proverbs made by Gruffudd Hiraethog (d. 1564), Oll synnwyr pen Kembero ygyd.
Also in 1550, a polemical text appeared under Crowley's imprint stating that it was "compiled" by Salesbury: The baterie of the Popes Botereulx, commonly called the high altare.
In this work, he took part in one the great controversies of the time, considering the doctrine of the sacrifice of the mass as show in the existence of stone altars in churches.
In 1563, an act of parliament ordered the bishops of Wales and Hereford to see that a Welsh translation of the Bible, Book of Common Prayer and administration of the sacraments be ready by 1 March 1567.
As Mathias points out, Salesbury's translations were heavily criticised for being full of Latinisms and other orthographical peculiarities and consequently unintelligible to many of his contemporaries.
[3] Sir John Wynn of Gwydir believed that Richard Davies and Salesbury were also collaborating on a translation of the Old Testament but disagreed over the use of one word.
Salesbury's last recorded work, Llysieulyfr ('Herbal'), was basically a paraphrase of some of the best-known herbals of the time, particularly Leonhard Fuchs's De historia stirpium.
Brinley Jones considers him the outstanding example of the Welsh Renaissance scholar, broad in his range and interests, inquisitive and enquiring.