T. W. Rhys Davids 
Vinaya Texts Translated From the Pali [PDF ebook] 

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. It was for use at such penitential gatherings that the text, now known as the Patimokkha, was composed. A list was drawn up – which of course it would be necessary from time to time to complete, and rectify of those offences which ought to be confessed and atoned for; this list was read out in the half-monthly meetings of the Order; and the Brethren and Sisters who were present were asked if they were innocent of each one of the offences therein mentioned. The use of such a list must have already begun in very early times. Tradition even ascribes the first laying down of each clause to the Buddha himself. This tradition is of course very far from being conclusive; but neither should we hold it impossible that the Patimokkha, either in its present shape, or at least in its most essential parts, can reach back to the Buddha’s own time, or to that of his personal disciples.